Remove all trailing whitespaces in the code tree

Just run:
 $ find -name '*.c' -print0 | xargs -r0 sed -e 's/[[:blank:]]\+$//' -i
 $ find -name '*.h' -print0 | xargs -r0 sed -e 's/[[:blank:]]\+$//' -i
Remove all effects code for a fresh and clean start
Add a simple unminimize effect the same as minimize
Add "effect_pending" flag

Initialized at META_EFFECT_NONE. The management of this should be done by
caller functions to effect functions.
Remove "icky" timestamp pinging on finish_minimize
Fix: the effect "finished" callback needs to be called after the effect ends

Added two fields to BoxAnimationContext to handle finish callback inside
box_animation_timeout function instead of effect_free. Now the finish
function is called after the effect is finished.
Implement animation handling in implement_showing

Functions meta_window_animate_[un]minimize will handle [un]minimization animations.
Maybe this should be done in effects.c file to trigger animations based on context,
compositing, preferences etc.
Bugfix: run finished function if animations are disabled
Bugfix: If the window shown was minimized, grab focus.
Bugfix: Correct was_minimized flag transition
Remove misleading comment in effect_free function

The new behaviour is the animation callback function should run the
finished function once it's done with the animation.