Sqlite3-to-mysql

* [FIX] fix regression introduced in v1.4.9

* [FEAT] add ability to change default text type using --mysql-text-type
* [FIX] fix BOOLEAN conversion to TINYINT(1)

* [FEAT] add support for DEFAULT statements

* [CHORE] fix tests

* [CHORE] add support for Python 3.10
* [CHORE] add Python 3.10 tests

* [FEAT] add CLI options for custom charset and collation
* [FEAT] add unicase custom collation
* [FIX] limit MySQL identifier to 64 characters
* [FIX] handle multiple column FULLTEXT index transfer error
* [FIX] fix multiple column index length 28
* [CHORE] move some MySQL helper methods out of the main transporter
* [CHORE] refactor package
* [CHORE] add experimental tests for Python 3.10-dev