Fix shadowMap count for directional lights

Splitting the view frustum yields splits + 1 frustums
Store the shaderNum instead of the shader pointer in the light interaction

This mimics what we do with draw surfaces
Fix r_showLightInteractions
Fix one small issue with .pk3 sorting – ‘.pk3’.

Its presence throws off the intended sort order, so it has to be
(temporarily) removed while sorting the .pk3 file names.
client-input/cmd: remove Cmd_AddButtonCommand

It was used to do +-commands, made a proxy command to handle that.
Also it reduces coupling between cmd.c and cl_input.c
Handle the case where no files in main/ are updated.
cl_input: fix 5b1d28cc0
Extend help menu.
Merge remote-tracking branch 'remotes/origin/master' into gameplay/master