Fix KeyPointMatcher

Since it's actually a distance, being named KeyPointMatcherTransform prevented
name lookup from working correctly
Avoid a mysterious crash related to closing VideoCaptures

Don't explicitly release the VideoCapture when it runs out of frames, further
investigation is needed, but this seems to cause an overrun or something

Additionally, make TemplateDataSource behave consistently with VideoDataSource,
breaking only after getNext has been called when no further frames are
available.
Add preliminary support for waitkey in Show2

This is currently implemented by an event filter on the QApplication, which
isn't great, but I couldn't get a QShortcut to work.
Add a 'byRow' option to Normalize, to operate on rows of a matrix independently