add fields/types and move the types in there.

fieldtype => Field Type
The one where I found out about toctree :hidden:
Turn it up to 11.
Merge branch 'dev' of github.com:pixelandtonic/Craft-Docs into dev

Conflicts:
	source/diving-in/fields/assets.rst
	source/diving-in/fields/types/multiselect.rst
	source/diving-in/fields/users.rst
Post-merge madness.
Merge branch 'dev' of github.com:pixelandtonic/Craft-Docs into dev

Conflicts:
	source/diving-in/fields/types/number.rst