in `$meta$measures$fun`

- re-implement d3e8ef0
- allow years up to 2150

until now, all fields were shown if
no argument was provided

the $extras$attribute_description field
in the meta-jsons of open.data can now be
read correctly for all 273 "valid" datasets

valid datasets are datasets that satisfy

* json$resources[[1]] == "csv"
* length(json$resources) > 1

The returned descriptions are not always consistent with the contents of
${opendata_id}_HEADER.csv because the
labels might be slightly different.

However, the codes always match and use the
same ordering

read_delim throws an error if the url for
the csv is passed as a character. Due to
differences in R<4.0 and the newest version,
this caused a bug in od_table()

- status code 200 never occurs
- check if raw object is empty rather
  than parsing it

- cache csv files in ~/.STATcubeR_cache
- only download data again if last_modified
  in json is newer than cache
- avoid nested loops for parsing
- exclude unnecessary columns in meta$measures
- make sure $data uses factors for
  classification variables

this affects two datasets, which are both
problematic with the current import logic.

- `OGDEXT_BINNENWAND_1` has no variabe
  codes in the first line of
  `OGDEXT_BINNENWAND_1.csv`
- `OGDEXT_VORNAMEN_1` contains fields
  of type <chr> like `F-VORNAME`

add column `label_en` to
- `$meta$database`
- `$meta$measures`
- `$meta$fields`
- `$field(i)`

this option affects
- the printing method
- the labeling of $data

TODO: language can be switched with
{object}$language <- {new_language},
however, `$data` is not updated in
this case

restructure sc_table to make it compatible
with the base class sc_data. In the new
version, the main part of tabulate() is
executed in the base class which provides
more flexibility.

- mixtures of fields with totals and without
  totals are allowed
- parameters can be specified as codes or
  as labels
- parameter raw can be used to return
  codes instead of labels

The sc_table class now also inherits
total_codes() and a more flexible
implementation of field()

$data and $meta are now parsed eagerly
which means that the slots are calculated
at construction time rather than the first
access

there was a regression regarding the
annotations parameter. Annotations are
stored as attributes in $data_raw and
dropped during aggregation. They currently
don't have priority and will be
re-implemented at some point

if the tibble package is attached, the data
will be printed with this class. These changes
do not cause a formal dependency to tibble
because they only reroute S3 dispatch if
the `print.tbl` generic is in the current
search path.

register s3 methods of pillar is available
with registerS3method(). ALternatively,
vctrs::s3_register() could be used

Also, export the print method for
sc_tibble_meta() and avoid warnings in
devtools::check() due to param inconsitency
because of missing ellipsis

use \uxxxx escape to print the ellipsis
in the footer of print.sc_tibble_meta

since this class is not exported and there
are no factory methods, use the classname
as the name of the R6 class generator object

the field $data_raw was renamed to $data and
the prevois $data is now only available via
$tabulate()

* use R6/roxygen2 to document the whole class
* move request time to $meta$source
* rename $raw -> $json
* advanced printing

* R6/roxygen2 documentation
* link ?sc_table_class from ?sc_table

od_tabulate() now only matches for labels
in the current language. If the language
of a table is set to "en", german labels
cannot be used. Update examples accordingly

when developing the R6 documentation,
it was shortly tested how the man pages
would look if the od_table class was
directly exported as od_Table. These
man entries mistakenly use this
invalid syntax

not related to od_table, but the old version
caused errors because of positional arguments
in R/table_custom.R#L27

the annotation parameter is not working
properly with the introduction of
sg_data which allows tabulate() to operate
via sums or via total codes. Use
if(FALSE) to skip this example for now

in the long run, it will have to be decided
how annotations should be aggregated in
$tabulate()

previsouly, this function expected sc_table
objects and now it operates with the base
class. This required some rerouting of the
different implementations and merging
of certain man-pages

the od_tabulate() function was removed from
the NAMESPACE because it would just be an
alias for sc_tabulate() at this point

the fact that the annotations param is broken
is now part of the class documentation
of sc_table_class