Fix outdated xref in docs.
Walkthrough of pending TODO 2.2 remarks

that were left there while doing major refactorings for 2.2. All such
TODOs have been either:
- implemented
- removed since no longer valid
- converted into a "regular" TODO since it's not a 2.2 specific concern
Reinstate files that were erroneously deleted during the release.
Merge pull request #3145 from nawroth/update-config-xref

[2.1] Fix outdated xref in docs.
Merge 2.1-maint -> master.
Merge pull request #3197 from neo4j/2.1-maint

Merge docs fix from 2.1-maint
DumpLogicalLog for lucene index not needed anymore
Prints before/after state for supported commands in toString()
Updating javadoc and refcard links in PDF. Adding a link to javadocs.
Merge pull request #3194 from tinwelint/todocleanup

[2.2] Walkthrough of pending TODO 2.2 remarks
Merge pull request #3200 from nawroth/update-relative-links

[2.1] Updating javadoc and refcard links in PDF. Adding a link to javadocs.
Merge pull request #3202 from neo4j/2.1-maint

Merge docs fix from 2.1 maint
first draft new cypher introduction