Add support for SQLite database

[zefir-git]

This PR makes it possible to choose between using SQLite or MariaDB for the database.

SQLite

SQLite stores all data locally in a file (by default bank.db, this is configurable). The advantage is that you do not need to set-up an external database server and manage authentication. If you wish to migrate the BankAccounts data from one server to another, you can simply copy this file to your new server.

This is the default option and works out of the box without having to set-up anything.

MariaDB

Using the MariaDB option allows you to connect to a remote MariaDB server. If you want to sync banking data between two servers using this plugin, you can use the same database on both servers. If you are developing a website or another plugin, you can also easily directly read all BankAccounts data from the MariaDB database.

To use this option you must set-up a MariaDB server, create a database and a user that is granted full privileges to the database.

[km127pl]

All looks fine to me, shading the entire org.xerial/sqlite-jdbc is a bit too much but you can't do much about it except using libraries/org/xerial/sqlite-jdbc in the server root, but it's unclear if it's always present there.
On git-Paper-22 the directory libraries/org/xerial/sqlite-jdbc/3.42.0.0/sqlite-jdbc-3.42.0.0.jar exists on first clean server startup

[zefir-git]

All looks fine to me, shading the entire org.xerial/sqlite-jdbc is a bit too much but you can't do much about it except using libraries/org/xerial/sqlite-jdbc in the server root, but it's unclear if it's always present there. On git-Paper-22 the directory libraries/org/xerial/sqlite-jdbc/3.42.0.0/sqlite-jdbc-3.42.0.0.jar exists on first clean server startup

Thank you for the suggestion. I have opened #12.