Multiple updates (syntax, indentation, code folding, snippets)

[gorriecoe]

@adrhumphreys A few changes here, so probably want to publish as a major version. vsce publish major should do the job.

Whats been done:

• Updated syntax highlighting.
• Updated indentation rules.
• Added code folding.
• Updated branding to match new guidelines.
• Added snippets via sanchez.
• Added settings to toggle comments and use items.
• General tidy ups.

Still to do:

• Sanchez will have another feature added soon which is node conditional checks to filter snippets. This may mean a minor update down the track.

Publishing: You may need to run npm run vscode:prepublish before vsce publish major. Its not really clear if that runs before hand.