Release v0.5.5

Changes:

• FIX: main loop crashes when table window is closed.
• FIX: deg/rad button does not work when scrtype=q
• FIX: zero incident energy not accepted even if QValue is positive.
• FIX: setting major ticks division fails for larger values.
• FIX?: setting number of major ticks sometimes fails.
• FIX: KShift does not become 0 for th3=pi because sin(pi)/=0 in rkcore.f90
• mass data manager now wont automatically load the newly created mass data as default and
  "Set as Default" button was added.
• mbox now uses QTextEdit to show message.
• M-key to toggle maximize/unmaximize plot window and result window.
• Right-Button drag zooms in/out in plot window.
• thetaStepBox replaced with QLineEdit to accept arbitrary number of digits.
• BUG?: mbox fails to show IbeamCursor after mouse button is pressed on.
• BUG: closing plot window crashes main (hard to reproduce).