Add CQL fillter and filter-crs query parameters

[dr-jts]

This PR adds query parameters filter and filter-crs, with filters expressed in the CQL text language.

Note: the CQL language parser is a direct copy from pg_featureserv. Ideally these will be kept in synch going forward.

CQL Support

CQL expressions supported are:

• property names (id, name)
• character literals ('foo', 'A text value')
• numeric literals ( 12, 98.678)
• arithmetic operators +,-,*,/ and % (modulo).
  • Subexpressions can be parenthesized to express evaluation order.
• binary comparisons (<,<=,>,>=,=,<>)
• property [NOT] BETWEEN a AND B
• property [NOT] IN ( value-list )
• property [NOT] (LIKE | ILIKE) pattern
  • pattern can include % wildcards
• property [NOT] IS NULL
• boolean combinations (AND,OR,NOT and (...))

Geometry Literals

POINT (1 2)
LINESTRING (0 0, 1 1)
POLYGON ((0 0, 0 9, 9 0, 0 0))
POLYGON ((0 0, 0 9, 9 0, 0 0),(1 1, 1 8, 8 1, 1 1))
MULTIPOINT ((0 0), (0 9))
MULTILINESTRING ((0 0, 1 1),(1 1, 2 2))
MULTIPOLYGON (((1 4, 4 1, 1 1, 1 4)), ((1 9, 4 9, 1 6, 1 9)))
GEOMETRYCOLLECTION (POLYGON((1 4, 4 1, 1 1, 1 4)), LINESTRING (3 3, 5 5), POINT (1 5))
ENVELOPE (1, 2, 3, 4)

Spatial Predicates

• INTERSECTS - tests whether two geometries intersect
• DISJOINT - tests whether two geometries have no points in common
• CONTAINS - tests whether a geometry contains another
• WITHIN - tests whether a geometry is within another
• EQUALS - tests whether two geometries are topologically equal
• CROSSES - tests whether the geometries cross
• OVERLAPS - tests whether the geometries overlap
• TOUCHES - tests whether the geometries touch
• DWITHIN - tests whether two geometries are within a given distance

Examples

https://localhost:7801/public.geonames.html?filter=type=%27LK%27

https://localhost:7801/ne.admin_0_countries.html?filter=pop_est%20%3C%202000000%20AND%20continent%20=%20%27Europe%27

https://localhost:7801/ebc.voting_area.html?filter=DWITHIN(geom,POINT(1000000%20400000),60000)&filter-crs=3005

Not included (yet)

• Temporal filters
• Documentation (can be copied from pg_featureserv)
• Multi-layer requests