Updating various files, creating a new class

Creates ConfigurationLoader class to prevent code duplication in
various places.

Adds control mechanisms to prevent invalid DBpediaResourceOccurrence
instances in the FileOccurrenceSource class. This is just a hotfix
so we can test new input files such as .tsv files using Context
information.

Modifies the IndexingConfiguration class to stop using a language
variable added to the stopWords file name.

Adds the new ConfigurationLoader class to a few other classes, this
centralises the initial configuration file loading step, and reduces
code duplication.

Fixes small warnings within the modified files.

Removes unused variables from the modified files.