Add multimaster mode

Add new mode "multimaster" aware. To run in this mode add parameter -Dmultimaster=true. Modifications:

• change SQLObject into abstract class, methods which handle parameters path, metadata, and conttenttype, constructors and method "save" is adjusted for cacheless mode.
• added tests. To run test, it is best to use IntelliJ (it could add JUnit and correctly interpret project structure). Steps to prepare env:
  • create clear database
  • adjust parameters in init_db.sh (it would compile sql.jar and initialise database for multimaster mode)
  • later open tests in IntelliJ. It should suggest adding JUnit to class path - accept it
  • run tests in SQLObjectTest and SQLObjectCachelessImplTest

Todo:

• performance tests, how much it would fall down
• add correct JavaDocs