fix android can't input unicode characters
fix hide soft keyboard by press 'back' button,
 then click current focus text edit/line edit control,
 soft keyboard won't show again

add features:
  press enter key with line edit control will hide soft keyboard
fix enter key
Merge branch 'master' into hotfix-android-unicode-ime-input
Move onKeyDown/onKeyUp from Godot to GodotView
Press 'back' button should not terminate program, normal handle 'back' event in game logic
Merge pull request #195 from sanikoyes/hotfix-android-unicode-ime-input

fix android can't input unicode characters