Consistent syntax scopes across language grammars

[chbk]

This has been a long-standing issue in Atom: creating grammars and themes is difficult because each language diverges with its own syntax scopes. More details in this PR.

The default syntax themes are already updated with the proposed conventions. There are documentation and language grammar PRs that are still open and can be merged into Pulsar.

I'm willing to help if there is an interest in fixing this.