range start is always left/bottom, etc.
Allow to specify alternative types for properties

This effectively replaces broken OrElse.
Merge pull request #1351 from bokeh/mattpap/alternatives

Allow to specify alternative types for properties
Merge pull request #1346 from bokeh/bugfix/623

range start is always left/bottom, end is always right/top
Remove 'type' property from guides
Remove data files from bokeh/tests (fixes #862)
Merge pull request #1353 from bokeh/mattpap/remove_guide_type

Remove 'type' property from guides
Merge pull request #1354 from bokeh/mattpap/862_remove_data

Remove data files from bokeh/tests (fixes #862)
add missing icon files
Merge pull request #1357 from bokeh/task/missing_doc_icons

add missing icon files
Merge remote-tracking branch 'origin/master' into mattpap/grid