[#1253] Change the titles to comply to our docs' guidelines
[#1253] Change "Organization" capitalization to comply with our guidelines
[#1253] Add text about the user/sysadmin guides on the index page.
[#1253] De-indent lists in the user guide.
[#1253] Remove redundancy and cross-link "Getting Started" and "Sysadmin Guide"
[#1253] Fix a few section titles' capitalization