SES-1677 (minor fixes): fix a regression of setting additional HTTP
headers in the SPARQLRepository (=> were mistakenly set as request
parameters instead of HTTP headers), add setUsernameAndPassword
convenience method as it is also available in HTTPRepository
Add tests for STOP_AT_FIRST_ERROR for NTriplesParser
Merge remote-tracking branch 'bitbucket/2.7.x' into 2.7.x
Remove STOP_AT_FIRST_ERROR from RDFParserBase.getSupportedSettings

In practice only N-Triples and N-Quads support it, so only mention it
there.