Adding missing include guards from some header files

Very sloppy in my part.  My C++ is getting rusty.
Adding HeaderOnlyTPl to the example (TriBITS #41)

This TPL will be used to test the TPL enable and failure logic.
Improving the error messages when TPL find fails (TriBITS #41)

This is the first step in improving the info for configuration TPLs and the
error messages when a TPL find fails.  Currently, I am only testing a
header-ony TPL but that behavior looks good.

A few things I did as part of this:

* The processing of TPLs now starts with "Processing enabled TPL" instead of
  "-- Processing enabled TPL" and I reduced the indent of the "--" lines by
  two spaces.

* It now shows what package eanble the TPL and makes it very clear how to
  disable the TPL and what impact that will have.

* The CMake processing no longer aborts with FATAL_ERROR inside of the
  TRIBITS_TPL_DECLARE_LIBRARIES() function.  Instead, it sets a global var
  TPL_${TPL_NAME}_NOT_FOUND=ON and does a RETURN().  Then, the calling TriBITS
  code checks this and then prints more info and then aborts.
First step in changing name to TRIBITS_TPL_FIND_INCLUDE_DIRS_AND_LIBRARIES() (TriBITS #41)

This commit is so that git will be able to follow the file rename.
Changing name to TRIBITS_TPL_FIND_INCLUDE_DIRS_AND_LIBRARIES()

This is a much better name for this function.
Breaking out TribitsProcessEnabledTpl.cmake (TriBITS #41)

This will make it easier to add unit testing for the
TRIBITS_TPL_FIND_INCLUDE_DIRS_AND_LIBRARIES() function.
Adding infrastructure for automated testing of TribitsTplFindIncludeDirsAndLibraries.cmake (TriBITS #41)

I now have the infrastructure to be able to quickly test the full functioning
of TRIBITS_TPL_FIND_INCLUDE_DIRS_AND_LIBRARIES() in fast little unit tests.

I added a new mock TPL HeadersAndLibsTpl with empty header and library files
that the CMake commands FIND_PATH() and FIND_LIBRARY() seem to work wtih.
These commands are run as cmake -P scripts

This test shows that FIND_LIBRARY() does not look inside of the library files
at all, it just looks for the file names based on the prefix and suffix.

After this I will add a bunch of unit tests to assert the behavior of
TRIBITS_TPL_FIND_INCLUDE_DIRS_AND_LIBRARIES() for as many cases as I can think
of.
Improved lib failure msg, fixed tentatively enabled TPLs, added more test cases (TriBITS #41)

I have now improved the failure message when libraries can't be found to match
what they look like for header file include dirs (which was the goal of
TriBITS #41).

My prior refactoring to improve the TPL failure message broke the tentatively
enabled TPL feature.  I now have good test cases to show that it now works.

I also added a few more test cases for the most typical use cases.

There is still a good bit more testing needed to pin down every use case and
behavior but I feel a lot better about this code than before I started this
refactoring work to improve the TPL error messages (TriBITS #41).

Fixes TriBITS #41
Explicitly setting <Project>_ENABLE_SECONDARY_TESTED_CODE=OFF in PT default builds

Setting <Project>_ENABLE_SECONDARY_TESTED_CODE=OFF in the PT default builds
allows projects to set <Project>_ENABLE_SECONDARY_TESTED_CODE=ON by default.

Every project should really set <Project>_ENABLE_SECONDARY_TESTED_CODE=ON by
default since users should not have to know that the differences are between
PT and ST code.  Only developers should need to know the differences.
Fixing test for MPI case (extra MPI TPL in output) (TriBITS #41)
Merge branch 'better_tpl_error_msg_41'