Implement Doxygen front page concept, clean up documentation, resolve doxygen warnings

[skliper]

Checklist (Please check before submitting)

• I reviewed the Contributing Guide.
• I reviewed the CF README.md file to see if the feature is in the major future work.
• I performed a cursory search to see if the feature request is relevant, not redundant, nor in conflict with other tickets.

Is your feature request related to a problem? Please describe.

• Apply frontpage concept/documentation framework (mainpage can't be included in larger document)
• Clean up/clarify sections and apply suggested patterns
• Resolve warnings from building doxygen documentation

Describe the solution you'd like
See above.

Describe alternatives you've considered
None

Additional context

• Fix #2055, Refactor doxygen mainpage into frontpage cFE#2058
• Fix #2064, Use osal-common.doxygen to resolve OSAL Doxygen refs cFE#2065
• Fix #1227, Refactor doxygen and remove mainpage osal#1228
• Fix #1231, Doxygen strip path and expose common config osal#1232

Requester Info
Jacob Hageman - NASA/GSFC