More thorough testing of TMLanguage

[scripthunter7]

Tester should throw an error if the TMLanguage file is not structured correctly or if any regular expression is syntactically incorrect.
For both scenarios, the error message should be explicit and include the specific location of the error, indicated by row and column numbers.

In practice, incorrect TMLanguage is usually simply ignored and tokenization does not work.

For details on the TMLanguage structure, refer to: https://macromates.com/manual/en/language_grammars

Here's an example of an invalid regular expression:

match: |-
  (?x)
    (##)  # we often match separators, but in this case, first # in the separator considered as a comment - so we got an unbalanced parenthesis error