GDS Plugins: Start-Up Applications

[LeStarch]

Related Issue(s)
Has Unit Tests (y/n)
Documentation Included (y/n)

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Change Description

This PR makes several changes:

1. Adds a GdsFunction plugin with generic run function
2. Adds a GdsApp plugin with get_process_invocation function
3. Fixes CLI for argument parsing to add in plugin sections for arguments
4. Adds UTs for testing both plugin types
5. Straightens out naming for plugins
6. Adds Plugin class wrapper helper

Rationale

Users want start-up applications and functions

Future Work

Document this in fprime (github.com/nasa/fprime)

[LeStarch]

Also note: the plugin function definitions were moved within the classes they should return.

[thomas-bc]

I really like this new structure! LGTM