Converting documentation index to simple index.html file

It is silly to use DocUtils to generate a simple index.thml file.  Also,
DocUtils does not allow you to create multiple <a href="<link1>" PDF</a>, <a
href="<link2>" PDF</a>, etc. in the document.  This is stupid.

Just get rid of the fluff and have a simple index.thml file.
Removing assumption of a 'tribits/' base dir (Trilinos #6218)

Once I allow TriBITS to be specified as a package as <projectDir>/TriBITS, you
have to make this change for the tests to pass.
Allowing for abs pakage directories under project source dir (Trilinos #6218)

These changes were done in order to support Trilinos or other projects pulling
in TriBITS as a package from the absolute variable ${PROJECT_NAME}_TRIBITS_DIR
variable.

I added a pretty good unit test and updated the documentation.
Print out <Project>_TRIBITS_DIR

This is good info to print in the basic configure output.
Adding --no-rebase --no-append-test-results