Merge pull request #363 from KevWright/overviews

Added overviews section and docs.
Redmine #4733: Add documentation about CFEngine's line ending behavior
Document uiVersion as 3.6 addition to the API.
Note on support for legacy protocol in both server and agent
Merge pull request #364 from kacfengine/crlf

Redmine #4733: Add documentation about CFEngine's line ending behavior
Fix typo.
reference/functions/parsejson.markdown: fix parameters and document maxbytes
Merge pull request #365 from kacfengine/fix_typo

Fix typo.
reference/functions/parsejson.markdown: no maxbytes parameter, fix example
Added overview doc for Mission Portal.
Added see also links to MP overview.
Modified MP overview tag.
Edited some of the MP overview text.
Merge pull request #366 from KevWright/mission-portal

Added overview doc for Mission Portal.
Added install FAQ page
Added a main FAQ page that links to others.
Added more install FAQ Q&A
Added a glossary page.
Modified some spacing in Glossary.
Added a note about the system user for Postgres.