I18n: use id_windowmanager context for keymap idnames. Solves some issues with those names (notably "Clip" one, and "Screen" too) in some translations. Also move "Key" as "Keyboard" (opposed to "Keyframe") to same context.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@55568 954f8c5b-7b00-dc11-b283-0030488c597c