[KBSwitch] scheduleApply().
[KBSwitch] Expose keyboard models.
[KBSwitch] RulesStorage::GetKBModelCode().
[KBSwitch] Pass "-model" switch to setxkbmap.
[KBSwitch] Options loader.
[KBSwitch] OptionsConfigWidget stubs.
[KBSwitch] Handle keyboard options in KBCtl.
[KBSwitch] OptionsConfigWidget::{accept,reject}() impls.
[KBSwitch] Be a big boy, exec the setxkbmap app.