Update identity_management.rst: Content

Some blurbs about Active Directory & LDAP. I apologize if the build
fails again, but I'm having some trouble getting sphinx working.
Formatting Changes

Fixed the links and bulleted lists. Successfully ran make HTML with 0
warnings or errors.
Merge remote-tracking branch 'upstream/master'
Adding some basic nagios information.
Fixes typo, removes 80 char word wrap.
fixes line breaks, and removes additional comma
Merge pull request #148 from gpapilion/monitoring

Nagios information for monitoring_101
Updates later paragraphs to current style
Merge pull request #150 from gpapilion/monitoring_101_style_changes

Updates later paragraphs to current style
Merge pull request #124 from aytch/Windows-Identity-Management

Windows identity management