New option: colour-region-kill-ring-max

Also change colour-region-kill-ring to a ring structure,
and use delete-region instead of kill-region in colour-region-apply-kill

Altered items:
colour-region-kill-ring-max, colour-region-kill-ring,
colour-region-apply-kill
Use ring-insert in colour-region-apply-kill

Also only save colour-region instead of colour-region and text as before.

Altered items:
colour-region-apply-kill
New var colour-region-kill-ring-index and new func colour-region-kill-ring-rotate

Also fix other kill ring functions to use new kill ring

Altered items:
colour-region-kill-ring, colour-region-kill-ring-index,
colour-region-apply-copy, colour-region-kill-ring-rotate,
colour-region-apply-yank
New function colour-region-insert

Also comment out colour-region-apply-yank-pop for the moment.

Altered items:
colour-region-insert, colour-region-apply-yank
Update documentation for colour-region-formats

Also rename colour-region-apply-yank to colour-region-yank, make it interactive,
and use ring-ref to get item from kill-ring.
Bugfix: colour-region-insert & colour-region-yank

Altered items:
colour-region-insert, colour-region-yank
Bugfix: colour-region-apply-copy make new copy of colour-region

Altered items:
colour-region-apply-copy
Alter colour-region-apply-copy to just return copy

Change colour-region-copy to add the copy to the kill-ring.
Change colour-region-yank to insert a copy (so the one in the kill-ring is different).
Change colour-region-insert to just move the overlay as it now longer needs to make a copy.

Altered items:
colour-region-copy, colour-region-apply-copy, colour-region-insert,
colour-region-yank
Bugfix: use colour-region-apply-copy in colour-region-yank

Also rename colour-region-apply-yank-pop to colour-region-yank-pop

Altered items:
colour-region-yank, colour-region-yank-pop
New function colour-region-in-colour-region-p

Altered items:
colour-region-in-colour-region-p
Bugfix: update start/end info in colour-region-insert

Also check if in colour-region when calling colour-region-yank/yank-pop,
and emit error if so.

Altered items:
colour-region-insert, colour-region-yank, colour-region-yank-pop
Bugfix: colour-region-change-type

Altered items:
colour-region-change-type
Bugfix: rename func arg in colour-region-func

func arg in colour-region-func was being shadowed by func arg in
colour-region-apply-according-to-prefix
Renamed them to func1 and func2

Altered items:
colour-region-apply-according-to-prefix, colour-region-func,
Check overlay is valid in colour-region-apply-overlay

Altered items:
colour-region-apply-overlay
Add error handling code to colour-region-func

Dont break on error applying func2, just emit an error message instead.

Altered items:
colour-region-func
Check overlay in colour-region-apply-overlay

Make it more robust.

Altered items:
colour-region-apply-overlay
Update documentation in elisp file

Using org-readme-to-commentary command.
Update todo in documentation