Release of LenMus Phonascus version 5.3.1

LenMus Phonascus version 5.3.1 has been released. This version is focussed on
fixing bugs, in particular on those causing unexpected program termination.
This version also completes translation to Chinese and adds options
for clefs reading exercise:

• Full translation to Chinese.
• Changes in exercises to display more messages to guide users.
• Added options to clefs reading exercise for choosing clef and notes range.
• Bug fixes:
  - Occasional program termination when moving to another exercise.
  - In compare interval exercise the option to start both intervals
  with same note was not working.
  - In interval exercises sometimes an strange error message saying
  that 'Not possible to generate valid interval' was displayed.
  - Button colour was removed as soon as mouse moved over the button.
  - Other bug fixes and changes related to exercises.
  - Moved to Lomse library version 0.14, as it fixed many bugs.
• Technical changes: Logger class removed and replaced by Lomse logger.