Add DB connection properties environment variables

[efim-a-efim]

I think it will be perfect to add an ability to specify external DB connection properties (JDBC connection string) through docker environment. Currently this image breaks JetBrains best practice to use external DB for production purposes.
Maybe this task will require adding all DB drivers to this image.

[VladRassokhin]

Before doing docker run you could place proper database.properties file into <TC DataPath>/config/
As <TC DataPath> would be mapped inside container, TeamCity should properly read and apply it

[vshuraeff]

@VladRassokhin this is not docker-way
where we get this file? or it can read any random format?

[VladRassokhin]

@Svolentin Contributions are welcomed.

Example files can be found as <TC_Data_Dir>/config/database.*.template on running TeamCity server.
More details in documentation.