ENH: Added wait* methods to iohub Keyboard device

The psychopy.iohub.client,Keyboard device now has the following methods:

* waitForKey(...): Same idea as event.waitKeys(), but supports same
filter args as keyboard.getKey(....)
* waitForRelease(..)
* waitForPress(...)

Also changed these emthod anmes in the class:

* getKeys -> getKey
* getPresses -> getPress
* getReleases -> getRelease

Also added cls method to visual.Window that pumps all psychopy windows
for pyglet events to wrap code that is used in a few places.