maintain and is only going to get worse as more are used. So instead, add a new
uint64_t member to cmd_entry which is a bitmask of upper and lowercase options
accepted by the command.
This means new single character options can be used without the need to add it
explicitly to the list.
- change the one layout function into two _refresh and _resize
- create layout-manual.c for manual layout code
- move the fit panes/update panes code from window.c to the new file as it is only used by manual layout now
- move the resize pane code into layout-manual.c as well
- get rid of the direct calls to fit/update and make them go through layout
- rename a couple of variables
This is mainly as a first step before reworking the manual layout code to see if anything breaks.
