Added icon, and embedded fonts in SVGs
Fixed element list
Applies icon size property
Displays icon for element picker action
Fixed progressbars by hooking into hyperspy

By overwriting hyperspy.misc.progressbar.progressbar, we coopt the
progressbar code, and display a QProgressDialog instead of the terminal
progress. DummyProgresses are still used as before.

Made it thread safe so it can be used on both main thread and in
background thread.