Mnemosyne 2.7.2 ready for testing

[Peter Bienstman]

https://www.dropbox.com/sh/rudvbzywm1pczg2/AADRtPWsITbEuRmkEVQkASyEa?dl=0

- Wrap tag string so that it no longer stretches the application window.

- Don't crash when using saved sets containing over 1000 tags (reported

  by abacus).

- Android: don't crash when trying to star a card when no card is showing.

- Improve robustness of Windows sync server.

- Enabled Icelandic text-to-speech.

- More robust detection of Latex on OSX (patch by Devin Howard).

- Exposed more functionality of libmnemosyne to scripting programs.

- Update example plugin to change keyboard shortcuts (requested by Garrison

  Taylor).

- Upgraded to PyQt 5.15.0, matplotlib 3.2.2.