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
Docstrings like this can fit on a single line.
```python
def list_profiles(self):
    """Returns a list of available profiles on file."""
```