Revert "Added index method to InstructionGroup"

This reverts commit cc9af2bb191338f31225c192df9739a28e29f197.

This commit only duplicates the functionality of
InstructionGroup.indexof.
Fix not looping issue in uix/video.py
Added appropriate documentaion for eos
Ammeded the docs for more accurate summary
texture: add icolorfmt parameters to define alternative color format storage. Added red, rg as possible colorfmt, and r8, rg8, rgba8 as possible icolorfmt. (needed for SMAA widget)
Make property list draggable by scrollbar too
doc: revisions to graphics/vertex_instructions.pyx
Add more details in stacklayout doc.
Merge branch 'master' of https://github.com/kivy/kivy
revert partial changes for  690324e. Removel of
`convert_distance_to_scroll` was unintended.
closes #1896
increase scrollbar width
Merge pull request #1897 from voen/patch-2

Make property list draggable by scrollbar too
doc: add instructions for Raspberry Pi
- properly unset the selected_node attribute, which addresses issue #1898
- addresses issue #1839
doc: update gettingstarted image to add raspberry pi
Merge pull request #1902 from aspidites/showcase_crash_fix

- addresses issue #1839
doc: grammar correction in uix/widget.py
fix: added blank line to fix doc build
doc: changed to standard version tagging