Check for both headers and libs before making test prog

Previously, it was assumed that the project was available if only the
libraries were found (either by full compile, or by package).
Merge pull request #144 from rolk/0144_ert_notfound

Configure complains about errors in CMake file if ERT library is not found
Don't reset list of tutorial programs after filtering

The list of tutorial programs were filtered on whether UMFPACK was
located or not, but then the list was reset to the original again
just before compilation starts.

Also corrected a minor spelling error which caused a similar error.
Merge pull request #143 from rolk/0143_umfpack

build fails if UMFpack development package is not installed