PrimarySearch: Use Solr (embedded or not) to retrieve documents based on clues

AnswerGenerator has been appropriately modified to generate just two
answers per result.

We are currently testing this on data/guten from blanqa.

Currently, we depend on SolrWrapper of oaqa. In the future, we will
likely want to switch to SolrJ.
desc.type.Constituency.xml: Our own copy that adds a missing PRN type

Borrowed from upstream. Waiting for new dkpro release...
BerkeleyParser: Our own copy that can handle parse errors

Borrowed from upstream. Waiting for new dkpro release...

We would immediately crash when trying to process wilder data sources
like Gutenberg.
ClueGenerator: Do not use super-common-word SVs
PrimarySearch: Multiple fixes regarding creation of separate views
Add an extra ResultAnalysis pipeline step

Comes with CandidateAnswer FS and a simple sentence filtering already.