-- now we have completely removed the dependency from google::sparsehash and migrated to absl.

-- Note that so far, no unescaping is performed.

- Transitive Paths use HashSets which now also have undefined orderings with absl. Tests don't rely on this anymore

- The case, where a prefix was used with an empty "content" (e.g. <a> wd: <b>) was broken before,
  luckily there was a unit test and this is now fixed.

…TL file.

- Previously there was a "parsing of ttl has failed, but there is still content left" warning, although
  the remainder of the ttl input was only whitespace.

- This was due to a bug in the Parser's skipWhitespace() function which failed if the input consisted of ONLY whitespace. This is now fixed.

…ashSet

# Conflicts:
#	src/parser/TurtleParser.cpp
#	src/parser/TurtleParser.h

- also apply the normalization of literals correctly during index build time
- Adapt the Index unit tests to "legal" knowledge bases
- Disable the CTRE parser for now, since it becomes awefully slow with the PnameNS and PnLocal changes for some reasons.
- TODO: Maybe we want to renable the CTRE Parser with the old "wrong"
  behavior as a very fast way to parse Wikidata