Improved auto-alignment of exported equations (TeXExporter)

Updated to MMA 12.1, improved TeXExporter

- better autoalignment of equations
TODO:
- implement \begin{cases}
- fix bugs with bold equations

Improved Anki Export

Added options to “Anki” button

- Fixed a bug with “<“ sign, now it is exported as \lt

Small usability improvements

'Custom' button added to the toolbar TeX button

Initial release

Project renamed and reorganized into Paclet with subpackages TeXExport and AnkiExport.