Keep controls visible in image viewer on resize

Also, by calling setMinimumSize() on the ImageCanvas, ensure that the
canvas as a whole is correctly resized. Getting the contained image to
resize properly is a task remaining.

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14260 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd