NUTCH-1870 XSL parse filter

[sebastian-nagel]

• apply patch contributed by @albinscode
• load configuration files from classpath and address thread-safety

Note: not ready yet:

• TODOs in code
• unit tests fail (with DOM built by tagsoup parser)
• see also open points in NUTCH-1870

[balashashanka]

Hi @sebastian-nagel, was going through this. Out of curiosity why hasn't this still merged? I see in the discussions everyone is ok with the code. And it doesnt have any merge conflicts.

[sebastian-nagel]

See the TODOs in the comment here and Jira.