COMP: Ensure FindDCMTK module works with and without DCMTKConfig.cmake file

In the case the provided DCMTK build or install tree doesn't have a
DCMTKConfig.cmake file, the first call to "find_package" should fail
quietly so that it doesn't prevent the rest of discovery process from working
as expected.

See #329
COMP: Make FindDCMTK more verbose

It will display the following text:

-- Trying to find DCMTK expecting DCMTKConfig.cmake
-- Trying to find DCMTK expecting DCMTKConfig.cmake - failed
-- Trying to find DCMTK relying on FindDCMTK.cmake
-- Trying to find DCMTK relying on FindDCMTK.cmake - ok
Merge branch 'update-find-dcmtk-to-support-no-module'
Added display tables to DICOM database schema; Merged from lassoan/276-dicom-database-display-tables
Update display fields method body implemented
Added skeleton of ctkDICOMDisplayedFieldGenerator and a few example rules
Merge remote-tracking branch 'remotes/cpinter-commontk/276-dicom-database-display-tables' into 276-dicom-database-display-tables

Conflicts:
	Libs/DICOM/Core/ctkDICOMDatabase.cpp
	Libs/DICOM/Core/ctkDICOMIndexer.cpp
	Utilities/CMake/FindDCMTK.cmake