68 epics key error for epuangle device and progressive stack serialization error

[RussBerg]

General:

• removed unused icons directory
• restrict nx_server log size and location
• added a reset to base data directory button for contact sheet (data viewer)
• strip tool scaling now set in beamline config .ini file
• removed pixmap delegate from scan queue progress widget
• common code to load a NXstxm hdf5 file now skips the instrument folder in the data and returns only the data specified in the 'default' attributes

BlueSky:

• disabled progressive stack in beamline config .ini file, design needs rethink to avoid random json serialization error
• added sim devices

Pixelator:

• specify when to update the scan plot as a percentage of scan completion to improve plotting performance
• fixed scan progress reporting to scan queue progress widget
• default sample scans to "Constant Velocity" instead of "Point by Point"