Implemented the creation of one thumbnail per page for multi-page file
types.
Removed 3 obsolete versions of JUnit from the lib folder.
Adapted implementation of generateThumbnails to also work with image
files (only 1 thumbnail will be generated). This operation always writes
thumbnails into a subdirectory.
Fixed passing of width/height parameters to PDFBoxThumbnailer instances
that are created to generate thumbnails from office documents.
Removed sysout statement.
Changed logging dependencies to enable running all logging via SLF4J.
This allows developers, that use the standalone version, to make the
final choice of logging facility for their applications.

Changed jodconverter to a homebrewed version containing a fix for the
lookup of the soffice binary on Mac OS X.

Updated the versions of pdfbox and fontbox to 1.8.6.
Added the unoloader.jar that the build script was looking for.