Release 3.4.3

Changes

• lib: add 'sync' argument to merge and concatenate methods
• gui: use ui without generated py files
• GUI can run with PyQt4 as well now
• gui: change line style on the current plot
• gui: make sure the cursor remains visible when moved using the left and right keys

Fixes

• fix setup.py to properly include files needed for GUI
• lib: fix MDF3 error when the file header had no comment