Improving Developer 3_Developer_Guides

Improving Developer 3_Developer_Guides

Worked on creating new services and applications.
1. Removed Fixme file
2. Formatted some text and numbering
3. Fixed some broken links.

Bug-AGL: [SPEC-4470]
Signed-off-by: Vinod Ahuja <vahuja@unomaha.edu>
Change-Id: If3f9a171faff8466bd6d141f9537cd98468fadbb
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/documentation/+/27993
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>
Tested-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>