Create Concepts directory and move Arch, Design, and Components into it
Merge pull request #289 from deb-cfengine/concepts_dir

Create Concepts directory and move Arch, Design, and Components into it.
Update categories to correct missing Arch files.
Merge pull request #290 from deb-cfengine/concepts_dir_fix

Update categories to correct missing Arch files.
Removed Mission Portal link on 2 pages because it no longer exists at cfengine.com.
Merge pull request #291 from deb-cfengine/MP_link

Removed Mission Portal link on 2 pages because it no longer exists at cfengine.com.