Add autocompletion and snippets

Add autocompletion for the \lilypond command and snippets for the \begin{lilypond} environment and \lilypondfile commands.
Further autocompletion and snippet work.
Allow LyTeXTools delimiters on same line as other material.

Search for delimiters is now performed with regex patterns. Fixed an borderline-case SyncTeX bug. Switched off console logging for release.
Major revision. See release notes.