`emacsclient` started with `-c` or `-t` argument create a new frame that shall
not be used to manage X windows.
Also fix some related input focus issues (with some remaining unfixed).
Close#17.
* Relax the conditions to refresh layout; this may introduce some overheads
though
* Fix the problem when `*scratch*` buffer is killed; close#12
* Enhance `exwm-reset` by forcing layout refresh in it. This should allow users
to overcome some layout bugs
