remove quickcheck from the testdependencies

it spilled a warning about not being build for java 7
added tests for crate signal handling
fix tracking of active sql requests
upgrade crate-python used for tests to 0.12.0

in order to use the improved CrateLayer
Merge pull request #1178 from crate/m/process_tests

M/process tests
renamed NullType to UndefinedType in order to avoid confusion
Merge pull request #1181 from crate/h/rename-nulltype

renamed NullType to UndefinedType in order to avoid confusion
updated changelog according to 0.44.0 release
don't use xcontent to set fetchSourceContext/version on SearchContext

this breaks "where _score" as minScore isn't set
anymore on the SearchContext.
build lucene query directly from symbols
support minScore in LuceneQueryBuilder
support type missmatches in EqOperator
use LuceneQueryBuilder also for group by queries