Feature/pdf export

[TwoOfTwelve]

Adds the ability to export pdfs from JPlag.

The pdf generation is done in a separate module and doesn't affect the rest of JPlag. For testing purposes the CLI automatically exports the overview and the first 10 comparisons as PDFs.

The code isn't ready to be reviewed yet, but let me know what you think about the PDFs.

TODOs:

• Cleanup code
• Export clusters
• Add UI features for exporting the PDFs
• Implement syntax highlighting for the most relevant languages
  • Java
  • Python
  • C/C++

The PDFs generated with the PROGpedia dataset:
comparison_00077_00001-00131_00005.pdf
comparison_00005_00002-00131_00005.pdf
comparison_00111_00001-00178_00002.pdf
comparison_00111_00001-00137_00002.pdf
comparison_00111_00001-00153_00001.pdf
comparison_00111_00001-00133_00001.pdf
comparison_00111_00001-00145_00001.pdf
comparison_00111_00001-00127_00002.pdf
comparison_00111_00001-00125_00001.pdf
comparison_00111_00001-00177_00003.pdf
overview.pdf

PDFs for the CLI module compared with itself:
comparison_cli1-cli2.pdf
overview.pdf

[tsaglam]

I had the time to take a look attached PDFs. Here is some random feedback:

• The font size in the file tree should probably be smaller, so all files are usually one a single page (see the CLI pdf)
• I still think that side by side comparison on landscape pages might be interesting to look into