Update rulesets.rst

Updated text
Update rules.rst

Update title/text
Create ruleset-development.rst
Create using-rulesets.rst
Update rulesets.rst

Updated text
Update standard-ruleset.rst

Updated text, and included ruleset details
Update standard-ruleset.rst

Updated text
Update ruleset-development.rst

Updated text
Update and rename using-rulesets.rst to ruleset-spec.rst

Ruleset spec added
[#156] Remove some pages/text

Some of this Steven couldn't remove through GitHub's web interface, and
some has been manually copy/pasted from other documents, when it should
be copied automatically into the built documentation instead.
Merge pull request #207 from IATI/SF-ruleset-documentation

Sf ruleset documentation