weston-wfits: Separate different input modes into classes

This encapsulates the logic in specialized classes and will
make it easier to add new input modes.  It also enables us to
add functionality to allow runtime/dynamic selection of the input
mode.

Signed-off-by: U. Artie Eoff <ullysses.a.eoff@intel.com>
weston-wfits: Move module_init to its own file

Signed-off-by: U. Artie Eoff <ullysses.a.eoff@intel.com>
weston-wfits: move destroy listener to init file

Signed-off-by: U. Artie Eoff <ullysses.a.eoff@intel.com>
weston-wfits: split logic into separate files

Split the logic for the different wfits interfaces into
separate files.  Used classes to encapsulate logic but was forced
to use primarily static members/functions since Weston has a
bug that results in a detrimental side-effect of destructing
objects that are loaded when it fails to fork/exec client
processes (e.g. weston-keyboard, weston-screensaver, etc.).  That
is, when Weston fails to fork/exec it calls exit(-1) instead
of _exit(-1) and hence invokes atexit and destructors for the
cloned objects in its forked process.  Those destructors might
unload/uninitialize things that effect the main process (e.g.
sockets, ioctls, etc...).

Signed-off-by: U. Artie Eoff <ullysses.a.eoff@intel.com>
weston-wfits: rename input-emulator-server to input-emulator-notify

Signed-off-by: U. Artie Eoff <ullysses.a.eoff@intel.com>