Modularized virtual schema common parts

Refactoring

• #1 Updated a module description and dependencies.
• #9 Removed deprecated lines of code.
• #10 Replaced Exception and RuntimeException with more accurate types of Exception.
• #14 Removed commented code.
• #15 Fixed sonar findings:
  -Removed duplicated code;
  -Decreased complexity of the certain classes;
  -Replaced assert lines with proper checks;
  -Added try-with-resources blocks instead of calling close() method etc.
• #20 Declared local variables, fields and method parameters as final where it was possible.
• #29 Fixed the bug where method getType() of SqlPredicateIsNotNull class returned the wrong type.
• #25 Improved unit tests coverage.