Rainbow neu

[stevesims]

Incorporates most of the changes from the "rainbow" MOS that @tomm has been experimenting with

To briefly summarise, that includes:

• changes/fixes from @breakintoprogram (added to the Quark codebase since 1.04 - currently unreleased)
• "comment" commands from @sadbeast
• enhanced VDU command from @HeathenUK
• tab command completion from @HeathenUK
• hotkey support from @HeathenUK
• support for a bin directory from @HeathenUK
• directory listing enhancements from @tomm

Also includes:

• some minor fixes
• smarter "help" command
• confirmation step for wild-card delete
• line editor now supports flags to control whether tab-completion, hotkeys and history are enabled

The current intent is that this will form the basis of a new 2.2.0 MOS release

[stevesims]

Current blocker on this PR is that the tab completion functionality occurs everywhere that the MOS line editor is used. This means at any BASIC input prompt (whether that is the BASIC CLI or an INPUT statement prompt)

ideally tab command completion should only occur for MOS CLI

arguably the line editor history should be opt-in too - right now it is also active for the BASIC CLI (which is probably fine) and BASIC INPUT statements (not so fine?)

the enhanced line-editor behaviour is now all opt-in, and the existing history behaviour can be opted out. this is done in a backward compatible way, via changing the meaning of the "clear" flag to be a bit-field, thus the existing "0/1" values for that flag as per the documentation will still work