Add libjpeg dependency for libtiff and minor changes.

It is possible to build libtiff with libjpeg-based JPEG coding support.
Thus CMake is told on Unix to add libjpeg includes and libraries so that
tiff-based tools will be linked to libjpeg, too. This mirrors the
./configure behaviour under Unix. It is not tested whether libtiff
actually was compiled with JPEG enabled. Additionally, the "QUIET" option
was added to avoid CMake's FindModule scripts printing messages about
external libraries that are already covered by explicit DCMTK messages.
Re-ordered code for some external libraries.
Fixed issue with missing terminating NULL byte.

Fixed issue with possibly missing NULL byte at the end of wide character
strings in getDirNameFromPath() and normalizeDirName().
Always use OFFilename() instead of "" as a default.

Always use OFFilename instead of "" (empty 8-bit character string) as a
default value in order to make sure that wide character support under Windows
really works. This is because "" only initializes the char* member variable
of OFFilename and not the wchar_t*.
Use printError() instead of OFLOG_FATAL().

Use OFConsoleApplication::printError() instead of OFLOG_FATAL() in case of a
missing command line parameter.
Fixed further issues with wide char support.
Fixed shared library build under Unix (configure).

dcmimgle and related external libraries have not been linked to dcmrt
applications in case shared library option was enabled and a configure/make
build was performed under Unix.
Allow empty file-set ID in DICOMDIR (type 2).

Allow file-set ID to be empty in a DICOMDIR since it is type 2. Also fixed
spelling ("file-set ID" instead of "file set ID" or "fileset ID") where
relevant, i.e. in log output and syntax usage.
Fixed dll build on windows.

Created a workaround for Visual Studio that disables dll storage specifiers
when linking directly into the executable. This is needed since the
built-in dictionary code is created by the tools mkdeftag and mkdictbi and
thus those tools statically link the few required dcmdata source files
instead of linking to dcmdata as a whole.
Correction of inconsistent previous commit.