Added example code in Sitemap

I have added an example code about the possibility to use the sitemap
module in custom modules.
So user do not need anymore to look in the system module to understand
how it works.
Hope I didn't make errors in the text!
added form_data parameter to the pre_save method in developer docs for field types
Merge pull request #120 from heylookltsme/2.2

small change to developing-field-types/methods.md
Merge pull request #119 from ChristianGiupponi/2.2

Added example code in Sitemap
Work in progress docs.
More information on PyroCMS URLs.
Defining some styles for samp and dfn.
Updates to the API index and streams driver.

Still getting a handle on using dfn, var, and samp. Those may change.
We're not actually adding Grid to the core.
Adding link to full server requirements in the getting started guide.
Git workflow page.
Merge branch '2.2' of github.com:pyrocms/pyrocms-docs into 2.2
Merge branch '2.2' of git://github.com/pyrocms/pyrocms-docs into 2.2