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
- 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
doc: restored python highlighting to remove red error surrounds
doc: layout/tag fixes to uix/gridlayout.py
Correct label padding to be positive, not negative.
doc: fixed version changed spacing
doc: corrected versionchanged spacing + small grammar corrections
doc: corrected versionchanged spacing for _event.pyx
doc: corrected versionchanged spacing for adapters/listadapter.py
doc: corrected versionchanged spacing for core/text/__init__.py
doc: corrected versionchanged spacing for core/window/__init__.py