Handling of surrogate characters in Revisionmachine

[rzo1]

Copy pasted from the README.

There are 4 possible modes of handling UTF8 surrogate characters.
Currently, the only reliable mode is "Discard Revision", in which any revision that contains surrogate characters is discarded.
The other three modes in "org.dkpro.jwpl.revisionmachine.difftool.data.SurrogateModes" have been disabled for now.
The corresponding config-section in the config tool has also been made invisible (org.dkpro.jwpl.revisionmachine.difftool.config.gui.panels.InputPanel)
The disabled parts are marked with TODO-markers

In order to use the other three surrogate modes, which try to handle surrogate characters differently,
the corresponding code has to be checked. Afterwards, the modes can be reenables in the config tool (InputPanel.java) and the SurrogateModes-class