Resolve "use database migration framework"

This Merge request resolves issue with manual db migrations. All script starting from version 12.1.0 will be managed by flyway library. Due to that all manual migration that were done starting from version 12.1.0 should be inserted into flyway history table (see the flyway_manual_init.sql) - this should affect only software developers who were working on version 12.1.0 up to now. Everybody who will start after MR is accepted wouldn't encounter any difficulties.

Regarding debian package. For now there is still manual migration and initialization of database, because there is no way to tell flyway what the previous version of database was. However, manual migration is limited to anything prior to 12.1.0. Further scripts will be migrated automatically by flyway.

Additionally there is new continuous integration test for checking if installation of debian package was performed properly and minerva website is available from localhost after installation.

Closes #389 (closed)