Add command for deleting node data

PuppetDB supports many commands, one of which is node deactivate, which causes the query API to stop returning results for a node. However, no data is actually removed until a GC sweep occurs. There are occasions when an immediate deletion of node data is desired and the only current option is to hit the DB directly with SQL statements, which is not great. Some examples are:

• Removing problematic exported resources.
• Removing old PE infrastructure nodes after migrating data from an old PE installation.
• Quickly clearing node data during testing.

PuppetDB should provide a command that allows for deactivation and immediate GC of data related to a specific certname, or certname pattern.