RelationshipGroup commands accept visitors

And also a windows-specifc fix for deleting indexes, similar to closing
neo stores after being memory mapped.
Simplify license info.
Merge pull request #2047 from davidegrohmann/2.1-loadcsv-periodiccommit

Try to only commit on row boundary when using Load CSV and Periodic Commit
Merge pull request #2042 from tinwelint/2.1-accept-relgroup

RelationshipGroup commands accept visitors
Merge pull request #2043 from nawroth/2.0-maint

Simplify license info.
Add configuration setting to stop Cypher from accessing local files
Adding newline to ensure tests pass on Windows
Merge pull request #2055 from systay/loadcsv-security-setting

Add configuration setting to stop Cypher from accessing local files
Report invalid clauses with FOREACH

Before semantic checking the clauses themselves
Merge pull request #2059 from cleishm/foreach-clause-check

Report invalid clauses with FOREACH
Merge remote-tracking branch 'upstream/2.0-maint'
Introducing TxCountsTrackingTestSupport

o  Moving PeriodicCommitAcceptanceTest to use FunSuite
Fix LoadCsvPeriodicCommitObserver must commit if updates are greater or _equal_ the batch size
Report line number information when failing during import with USING PERIODIC COMMIT LOAD CSV ...

o Some cleanup in EPB and renamed NullDecorator to NullPipeDecorator
o Introduce LoadCsvStatusWrapException
o Made sure LoadCsvPipe uses the correct external resource for loading (the one provided by the observer)
Ensure that each PeriodicCommitLoadCsvAcceptance test only turns green by exactly one way to commit

o Previously some of these tests could get green either by onNext() or onNotify() code paths which caused confusion.
  This happened due to the number of updates and the periodic commit value used and due to onNotify() using
  a batchSize * 2 safety factor
o Add UpdateCounter
Ensure that errors from server are correct when LOAD CSV adds line number information when USING PERIODIC COMMIT