CA-1176 allow children to be deleted without remove_child on parent

[dvoet]

Ticket: https://broadworkbench.atlassian.net/browse/CA-1176

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PR checklist

• I've followed the instructions if I've made any changes to the API, especially if they're breaking changes
• I've updated the RC_XXX release ticket with any manual steps required to release this change
• I've updated the FISMA documentation if I've made any security-related changes, including auth, encryption, or auditing

[coveralls]

Coverage increased (+0.2%) to 78.868% when pulling 99f5b3a on delete_child into 87df68e on develop.

[Qi77Qi]

So what is 'remove_child' action intended for?

[dvoet]

remove_child is envisioned to prevent a resource from being moved because a parent resource may want to enforce policies, etc. and allowing a move would allow escape from that enforcement