FEATURE: support both instance and volume tags

[astrostl]

Rather than an either proposition, expand it to work for both.

Specific use case: I have some detached volumes which get picked up by automated processes, so for that I want volume tagging. I also make everything with CloudFormation, which doesn't support the tagging of volumes upon creation. My workaround is to tag the instances, and then run a script afterward to tag all volumes associated with tagged instances.