Move all JIT attribute value parsing to the ExpressionParser

[fkleuver]

• Interpolation parsing currently happens in the TemplateCompiler. Moving this to the ExpressionParser allows interpolation expressions to be cached just like other expressions
• Semicolon-separated custom attribute values are not being parsed yet. This should be done by the ExpressionParser.
• Pass more context information (attribute type + binding command) to the ExpressionParser so it can make the right decisions about valid/invalid syntax.
• Implement loose vs strict parsing mode, where strict mode will detect and throw errors as early as possible (e.g. if a two-way binding command has a non-assignable expression, warn in loose mode and throw in strict mode?) (not appropriate for this scope)