Remove explicit error highlighting

[Arcensoth]

Removing the explicit "in-your-face" error highlighting should be considered for a variety of reasons:

1. Confusion: it has resulted in several bug reports, often regarding uncommon/obscure but valid syntax.
2. Inconsistency: the grammar is broad yet inaccurate, and there are plenty of errors that are not being highlighted.
3. Conflict: avoiding conflict with third-party formats that extend the vanilla mcfunction syntax is considered a bonus.

The alternative approach is to skip over violating syntax and leave it unclassified. Doing this may also fix the long-standing issue #32 with line endings, as well as #42 in that extraneous trailing characters will simply be skipped and not highlighted as an error.