add ogr plugin error handling to master/3.x
Merge pull request #2354 from kernelsanders/master

add ogr plugin error handling to master/3.x
Merge branch 'master' into custom-variant-2
use mapnik_value_type promotion traits for better type mapping
in symbolizer and params + move mapnik_value_type traits to
value_types.hpp
comment out implicitly_convertible<mapnik::value_bool, mapnik::symbolizer_base::value_type>();
make to_expression_string accept quotting char (default: '\'')
feature_generator_grammar - fix escaping