Simplify header inclusion and cmake list

[skliper]

Is your feature request related to a problem? Please describe.
Complex CMakeList.txt header logic shouldn't be needed any more

Describe the solution you'd like
Include the now "external" headers for tables

Describe alternatives you've considered
None

Additional context
Related to nasa/cFE#25

Requester Info
Jacob Hageman - NASA/GSFC

[jphickey]

Related changes here:

• The code should NOT include cfe_tbl_internal.h any more -- this is by definition an internal file, the tool does not and should not need to use any internal definitions from CFE_TBL.
• The references to CFE_TBL_MAX_FULL_NAME_LEN can be removed. Use sizeof(TableHeader.TableName) instead, and the alignment logic can be removed because the user should have defined CFE_MISSION_TBL_MAX_FULL_NAME_LEN as a multiple of 4 anyway.

[jphickey]

On second look, both cases of ByteAlignFileHeaders and the associated command line option should probably be removed. It has no purpose if we are enforcing that these values are a multiple of 4 already via compile time asserts.

[skliper]

@jphicky are you done with this one? If so could you submit a pull request with the associated testing details? It all looks good to me.