Disable renderers and select scale factor from command line
Move vertex_cache functions from .hpp to .cpp.
Add benchmark target to tests.
Simplify logic in vertex_cache.
Cache offseted lines. Reduces render times by 50% in certain tests.
Add copyright notices.
Include missing header.
Select tests by group.
Add benchmark mode.
Fix glyph widths after line breaking.
Fixes #1532.
Fix critial bug in text itemizer.

Itemizations is invalid after changing text, therefore lists have to be cleared.
Implement upright=right_only/left_only.
Closes #1533.
Show missing glyphs by rendering boxes instead of dropping the whole text.
Force strict mode for loading test maps.
Font directory.
Add missing reference images.
Update reference images for scale_factor 2.0.
Remove broken images for test "simple.xml" rendered with cairo.
Fix text rendering in grid renderer.
Update grid reference images.
Restructure shaping code in preparation for optimizations.