Fix #71, Moves interface definition files to inc

[chillfig]

Checklist (Please check before submitting)

• I reviewed the Contributing Guide.
• I signed and emailed the appropriate Contributor License Agreement to [email protected] and copied [email protected].

Describe the contribution

• Fixes Move interface definition files to "inc" location #71

Testing performed
make install
lcov

Expected behavior changes
No expected behavior change.

System(s) tested on
-Ubuntu 18.04

Additional context
N/A

Third party code
If included, identify any third party code and provide text file of license

Contributor Info - All information REQUIRED for consideration of pull request
-Justin Figueroa, Vantage

[jphickey]

Generally looks good to me, just one minor comment noted, but that does not really affect the fundamentals at all.

[jphickey]

Minor nitpick here, these actually do not need to be separate calls to target_include_directories ... they can be all listed in one call. Furthermore it might be more future-proof to reference the public includes via the ds target property, that is:

target_include_directories(coverage-ds_internal-stubs PUBLIC
    $<TARGET_PROPERTY:ds,INTERFACE_INCLUDE_DIRECTORIES>
)

This better follows the "DRY" principle - don't repeat yourself.... but it's not critical. Unfortunately that won't work for "src" because there is no property for that one).

I'd also suggest ditching the "utilities" subdirectory here - doesn't seem like it accomplishes anything except adding some build complexity, but that can be considered as a future enhancement, not related to this change.