Add new pasteboard history browser
Fallback on system pasteboard when history is empty

This is for the next/previous methods, the method that returns current already would fallback on the system pasteboard.
Use new pasteboard history browser

Closes #481
Introduce bundles::kItemTypeMost constant
Run will/did save and activate/deactivate callbacks in sequence

Previously only the most specialized callback(s) would run. For example creating a command scoped to “source” with “callback.document.will-save” for semantic class would never run for Ruby, Python, etc. because the Source bundle has a “Make Script Executable” callback scoped specifically to “source.ruby”, “source.python”, etc.
Allow disabling indent corrections when typing on empty lines

This is generally desired when the indent of a new line does not (necessarily) depend on lines above it, but where we otherwise do want indent corrections, e.g. HTML.
Remove unused API
Use proper iterate macro for temporary