Update documentation, and formatting alterations

Update documentation. Replace () arglists to nil.
Also fix interactive form of colour-region-change-comment

Altered items:
colour-region-create-new-type, colour-region-new, colour-region-next,
colour-region-previous, colour-region-copy, colour-region-kill,
colour-region-change-comment, colour-region-update-start-end,
colour-region-update-overlays, colour-region-kill-emacs-hook,
colour-region-kill-buffer-hook, colour-region-find-file-hook,
colour-region-initialize, colour-region-default-save-file
Squash code using new function colour-region-apply-according-to-prefix

New function handles prefix arg consistently for application in other
functions.

Altered items:
colour-region-apply-according-to-prefix, colour-region-copy,
colour-region-kill, colour-region-change-comment,
colour-region-change-type
Move colour-region-apply-according-to-prefix

Position it before other functions since it will be used by
many other functions.

Altered items:
colour-region-apply-according-to-prefix
More code squashing using colour-region-apply-according-to-prefix

Altered items:
colour-region-store-text, colour-region-toggle-overlay,
colour-region-toggle-text, colour-region-remove, colour-region-func,
colour-region-previous
Fix colour-region-copy and colour-region-kill

Use colour-region-apply-according-to-prefix with colour-region-apply-copy
and colour-region-apply-kill

Altered items:
colour-region-copy, colour-region-kill
Bugfix: colour-region-apply-according-to-prefix

Change current to cregion.
Also change colourregion to cregion in other functions to save a bit of space.

Altered items:
colour-region-apply-according-to-prefix, colour-region-apply-kill,
colour-region-apply-copy, colour-region-apply-yank
Bugfix: colour-region-apply-according-to-prefix

Pu last arg of apply function in a list

Altered items:
colour-region-apply-according-to-prefix
Tidy up comments and function docs
refactor: change colourregion to cregion