Becatrue/26/db mgr

[BECATRUE]

I implemented the 'Database manager` app.

When you click 'add' button, you can connect a new database. When you click 'remove' button, you can disconnect the selected database.

For example, I tested with the following process.

1. Add test.db.
2. Add test2.db.
3. Remove test.db.
4. Remove test2.db.

After step 2, the GUI is like below:

For test, I added a logging code in bus.py. The below is the printed logs about transferred messages.

{"db": [{"name": "test.db", "path": "C:/"}]}
{"db": [{"name": "test.db", "path": "C:/"}, {"name": "test2.db", "path": "C:/"}]}
{"db": [{"name": "test2.db", "path": "C:/"}]}
{"db": []}

[BECATRUE]

Please leave your opinion freely!

@kangz12345

[BECATRUE]

I applied all reviews except for namedtuple.

[BECATRUE]

I updated it again.

[BECATRUE]

I defined the namedtuple DB as a static variable not a field because I think it is not necessary that DB is an attribute of DBMgrApp.

[BECATRUE]

I updated! @kangz12345