Check functions - both WebAPI and CDS

[khufkens]

Still need to check all functions using the new integrated routines:

• WebAPI
• CDS

@retostauffer I follow roughly these guidelines mostly based upon rOpenSci experience with my MODISTools package:

errors

• forward errors from underlying services if possible
• trap all missing parameters

messages

• functional messaging, repeated statements of the same information to be avoided
• limit incremental info (see first point) which might fill a terminal when not properly refreshing

formatting of data, functions

• functional tidy data where possible (human readable, but machine parse-able)
• interface with other data formats when possible (hence me removing html output)
• limited fragmentation to limit overhead (more functions == more unit tests == more documentatoin == way more overhead in maintenance) for the same task
• exceptions to this rule are small helper functions for very specific tasks (complex feedback formatting, data shuffling etc)

documentation

• small worked examples are ok, i.e. basic but good documentation
• larger examples should go into the vignettes or "workshop" based documentation outside the package (specific use cases out of the scope of basic data queries)