Issue Description:

RHS parser rules are getting complicated while actually most of DRL keywords are not relevant in RHS.

To follow the current DRL parser implementation, we may accept a plain text in RHS and pass it as a consequence of RuleDescr.

It will have a drawback in Editor code completion in RHS. It will be addressed by a next JIRA.

Acceptance Criteria:

• Accept a plain text in RHS
• Simplify DRLParser.g4

Additional Information:

• Java syntax support is re-added by DROOLS-7516