Modularize keyboard XML files

* Remove duplicated xml-sw768dp/keys_apostrophe_dash.xml
* Separate keys_apostrophe_dash.xml to key_apostorhe.xml and
  key_dash.ml
* Separate key_space.xml from row_qwerty4.xml
* Separate key_f1.xml from xml{,-sw600dp}/row_qwerty4.xml
* Separate keys_f1f2.xml from xml-sw768dp/row_qwerty4.xml
* Fix incorrectly named rows_symbols{,_shift}4.xml to
  row_symbols{,_shift}4.xml

Change-Id: Id71967a016a348174d1fc265b654dbc233c6562e