Make interface to config options more flexible

[daleolds]

Previously all target options were saved as a struct. This required changes to the config target structure every time a new option needed to be saved. This commit changes target options to a generic hash and added generic interfaces to get or remove options.

Testing done:

• existing unit tests gave 100% coverage for new implementation
• manual testing $ ./priam login -a check ~/.priam.yaml $ ./priam logout check ~/.priam.yaml