[doc] Break out git based dynamic environments
[doc] Add generic documentation for dynamic environments
[doc] Reorganize dynamic environments documentation
[doc] Extract configuration documentation
[doc/dynamic-environments] Extract run use cases
[doc] Add dynamic environments ToC
[doc] Add community guides section for dynamic environments
Merge branch 'doc/1.2.x/dynamic-environments' into 1.2.x

This closes GH-125.
Merge branch '1.2.x'