Reorganize evdev plugins

Reorganize evdev plugins

linuxinput becomes evdevmouse. The experimental touch code is removed,
now the plugin's purpose is solely to generate mouse events from
absolute and relative pointer events.  The plugin key is EvdevMouse.

touchscreen becomes evdevtouch. The plugin key is EvdevTouch.

In case keyboard support appears some day, it will fit nicely in the
system by the name of evdevkeyboard or similar.

Some little udev code is moved to platformsupport so it can be shared
between the plugins. This may be extended later if more sophisticated
udev support is needed. N.B. the intention is to keep this as simple
as possible. We are shipping these plug-ins as reference examples, not
as full-featured drivers.

evdev and udev support has configure time tests from now on. This
means the "drivers" (generic plugins) will get built automatically
when the support is available.

Change-Id: Iaf6260b5c2edfb9f25d070d2764466725adc6b4e
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>
Reviewed-by: Samuel Rødal <samuel.rodal@nokia.com>