Add feature examples specing maintainers creating subgroups
Add feature examples specing maintainers creating subgroups

Both with subgroup_creation_level set to owners and to maintainers.
Also fixed the naming of some other examples in the same spec as they
were contradicting what they were actually performing in the test.
These examples were probably copy/pasted, and not renamed.

stoplightio/gitlabhq,stoplightio/gitlabhq,mmkassem/gitlabhq,stoplightio/gitlabhq,mmkassem/gitlabhq,mmkassem/gitlabhq,stoplightio/gitlabhq,mmkassem/gitlabhq