Visual Tests for issue mapnik/mapnik#1900

Conflicts:
	tests/visual_tests/test.py
refactor markers placements
fix markers transforms calc
fix include
Use points.csv instead of points.osm

- for mapnik/mapnik#1900
Merge pull request #2295 from mapycz/3.x-szn-markers-symbolizer

refactor markers placements
Merge pull request #2321 from plepe/bug-1900

Visual tests for issue #1900 (face-name and fontset-name in Format)
use detail namespace in json/geometry_generator_parser.hpp
Merge branch 'master' of github.com:mapnik/mapnik
Avoid -Wdelete-non-virtual-dtor warning
stop accidentally overwriting expected test images
visual tests: generate failure report even if you ctrl-c the process early
scons: fix first-run clean problem #2112
start passing fontsets down to format and layout - refs #1900
geojson - make feature_collection_grammar not dependend on mapnik::context
re-use feature_collection_grammar
fix symbolizer helper
c++11 - range based for loop (tidy)
opps - remove unused itarators decl
Merge branch 'master' of github.com:mapnik/mapnik