Description of problem:

Improve command line parsing routine such that users do not have to specify the full topic verb on the command line. Instead only enough should be required so as to differentiate the selection from other available topic verbs. A minimum of two characters should still be required.

For example `topic import` would become `topic im`, `topic export` would become `topic ex`, and `topic link` would become `topic lin` (so as to differentiate from `topic list`.