resolve warnings while compiling coreX11
Merge branch 'master' of https://github.com/kivy/kivy
core: improve reloading of images on context reload.
Add #:include directive. Implement circular reference guarding and sanity checks.
Merge branch 'master' of https://github.com/kivy/kivy into kv_include

merge master before pull request
Correct example
Add option to force-include which first unloads the file and then reloads it. Check for proper extension and inclusion status before any disk access takes place. Update example.
core:Factory raise Attribute if trying to access attributes like `bind`
core:WeakMethod test for reference error raised on python3
doc: revisions to graphics/transformation.pyx
doc: revisions to graphics/vbo.pyx
doc: revisions to graphics/vertex.pyx
doc: revisions to graphics/vertex_instructions.pyx
doc: revisions to graphics/vertex_instructions.pyx
Create PageLayout layout
style fixes
add swipe_treshold property
various improvements to pagelayout

add example in widget/
fix non-optimal algorithms
put simpler example in doc
update versionadded
doc fixes
uix:ActionBar fix comparison ref: #1729
setup: avoid gstreamer to be used on mobile (android and ios)