Expands ProfileManager and profile unit tests.

Adds methods for deleting, creating, and listing
profiles. Also modifies get_profile by adding
an extra arg to specify whether a non-existing profile 
should be auto-created.

Adds related unit tests to test_profile.

Methods added:
- create_profile
- list_profiles
- delete_profile

Related to https://github.com/Freeseer/freeseer/pull/632
I'd vote for list_profiles then. It's not consistent with the other naming, but it's not vague in any way and doesn't reuse any built-in identifiers.