DatePicker: datepicker_instActive released on instance destroy

Fixes #10668
Closes gh-1362
Autocomplete: Remove duplicate array key in demo

Ref gh-1363
Demos: Remove duplicate CSS properties

Closes gh-1363
Dialog: Remove leftover backcompat flag in tests
Core: Removed .focus( delay )

Fixes #9649
Core: Remove .zIndex()

Fixes #9156
All: Drop support for IE7

Fixes #9838
Closes gh-1365
Build: Upgrade to commitplease 2.0.0

commitplease now accepts "[tmp]:" and similar to temporary commits,
useful while updating pull requests that are squashed later.
Selectmenu: Remove broken tabindex code
Datepicker: Fixed month names and firstDay value in Arabic locale

Fixes #10035
Closes gh-1246
Build: Upgrade to grunt-git-authors 2.0.0 and add update-authors task

Closes gh-1378
Tests: Adding missing dependency
Tests: Removing unused visual theme test
Theme: Change default widget font-size to 1em

Fixes #10131
Closes gh-1374
Revert "Selectmenu: Remove broken tabindex code"

This reverts commit 1fb08790a6cae0ac861df0373a303d72ed0e8d71.
Selectmenu: Use native element's tabindex

Fixes #10665
Closes gh-1345