Fix #151, refactor HS to reduce complexity

[jphickey]

Checklist (Please check before submitting)

• I reviewed the Contributing Guide.
• I signed and emailed the appropriate Contributor License Agreement to GSFC-SoftwareRelease@mail.nasa.gov and copied cfs-program@lists.nasa.gov.

Describe the contribution
Reduces the cyclic complexity of various routines. This is a substantial refactor of the code, including splitting up the "monitors" source file into subsystem-specific implementation files (app, event, exec, etc).

Any function longer than ~100 lines is also split into smaller, more concise, less complex subroutines with separate documentation.

Fixes #151
Also related to #154

Testing performed
Run all tests
Manually send commands to verify FSW operation

Expected behavior changes
Better code complexity metrics, shorter files + functions

System(s) tested on
Linux

Contributor Info - All information REQUIRED for consideration of pull request
Joseph Hickey, Vantage Systems, Inc.

[jphickey]

NOTE: This also addresses a number of inconsistencies in the file structure/patterns where HS was not following the guidelines for what goes in each of the "config" files.