Documentation fixes: Consistent markup of boolean return values.

The core ruby docs use "true or false" so that is what I have gone with too.
Documentation fixes: Consistent use of "string".

Consistent with the core ruby docs.
Documentation fixes: Consistent use of "array".

Consistent with the core ruby docs.
Documentation fixes: Consistent use of "hash".

Consistent with the core ruby docs.
Documentation fixes: Consistent markup of integer return values.

The core ruby docs use "fixnum".
Documentation fixes: Miscellaneous consistency fixes.
Documentation fixes: Stop the licence being included multiple times.

Need a silly :stop and :startdoc: section at the top of modules where there are
no ruby statements between it and the licence comment above. Sigh.