Add info endpoint to provide information about CZERTAINLY application

[lubomirw]

Add /info endpoint to provide information about running CZERTAINLY application. It should provide following

• current version of Core as stated in pom.xml
• DB system and version (e.g. Postgres 12.1)

Note: It is worth to explore functionality provided by Actuator. If information provided by library are suitable for our needs, we should utilize it.