Textinput - Separate deletion and insertion / action keys handling (#5482)
Textinput - Separate deletion and insertion / action keys handling (#5482)

* refactored textinput::_key_down

* PEP8 fix: removed blank lines

* PEP8 fix: long if statement now on 2 lines

* fixed single-line enter issue

Cheaterman/kivy,rnixx/kivy,KeyWeeUsr/kivy,rnixx/kivy,KeyWeeUsr/kivy,kivy/kivy,bionoid/kivy,inclement/kivy,LogicalDash/kivy,matham/kivy,rnixx/kivy,Cheaterman/kivy,KeyWeeUsr/kivy,LogicalDash/kivy,matham/kivy,KeyWeeUsr/kivy,bionoid/kivy,inclement/kivy,kivy/kivy,akshayaurora/kivy,bionoid/kivy,matham/kivy,akshayaurora/kivy,kivy/kivy,matham/kivy,LogicalDash/kivy,Cheaterman/kivy,inclement/kivy,bionoid/kivy,Cheaterman/kivy,akshayaurora/kivy,LogicalDash/kivy