This change is made in the interest of allowing users to simply re-run
their init script at runtime without errors. Making this an error
doesn't really gain us anything.
This command takes a mode, modifiers, button/event name, and pointer
action as arguments. It stores these in the config data structure.
The currently available pointer actions are move-view and resize-view,
which replace the previously hard-coded functionality.
Closing the hovered view with middle click has temorarily been removed
until it is decided if we wish to make this another special pointer
action or perhaps allow running any arbitrary command (which would of
course include close).
