Fixes #158: Improving the download.sh script

Creates exports for various paths and useful constants.
  - Adds exports for every download URL used. This includes dbpedia,
  spotlight, opennlp, github (two links) and wikimedia related links.
  - Adds exports for useful locations. This includes the root data,
  dbpedia data, jena data, opennlp data, output data, wikipedia data
  and resources data directories.

Improves misc features
  - Adds support to Jena by creating a default Jena directory and
  adding TDB folders to all languages in order to keep the local
  stores.
  - Reorders the folders structure to be more intuitive.
  - Reduces the path/to/files using the exports mentioned above. This
  reduces confusion for developers using the script.

Adds basic functions to prevent code duplication.
  - Adds the function create_dir()
  - Adds the function download_file(). This handles common downloads.
  - Adds the function download_opennlp_file(). This function changes
  the file name to the english version if the original language file
  isnt found.
  - Adds a test_languages_array to validate the array with all the
  languages. This array is useful because after this script runs
  the folders for all languages will be created. This means that any
  language change inside spotlight wont require folder creation.

Modifies download URL paths of a few files.
  - Changes the download path to all previous sourceforge linked
  files.
  - Sets the stopwords and blacklistedURIPatterns download URLs
  to the Lucene quickstarter GitHub repository.
  - Sets the spot_selector.tgz and index.tgz download URLs to the
  dist module repository on GitHub.
  - Sets the http://spotlight.dbpedia.org/download related downloads
  to release version 0.5 until version newer versions have all the
  needed files.
Merge branch 'hotfix-indexing0.6.5' of https://github.com/Zaknarfen/dbpedia-spotlight into hotfix-indexing0.6.5