Parser updates

[simerplaha]

• Parser updates.
• Performance: Notice ExpressionParser.parse is called in multiple places where an Expression is required. The number of expression parsers executed need to be narrowed down to only the required expressions. For example, parsing a for expression with while expression for(while(); ....) is unnecessary. This optimisation is not a priority for now.
• Integration with CodeProvider can begin. Remaining parsers like enum, abstract, mapping, braces syntax etc., will be added later.
• Tests for some are still pending.
• Towards Parser errors prevent CodeProvider execution (completion, goto definition etc) #104.