Serialize identifiers in JSON representation of the Cypher execution plan description

- adding new ExtendedPlanDescription interface with the new needed API and compatibility wrapper for all compilers
Fix typo in package name
Reenable a test

- better comments on broken tests
- delete a useless ingored test
Updated documentation around performance tuning and execution plans
Further tweaks to tuning and execution plan docs.
Make the PageCache the only way to map files into memory.
Merge pull request #3605 from systay/tuning-docs

Updated documentation around performance tuning and execution plans
Merge pull request #3617 from davidegrohmann/2.2-reenable-test

Reenable a test
Merge pull request #3616 from davidegrohmann/2.2-add-ids-to-json-plan-desc

Serialize identifiers in JSON representation of the Cypher execution plan description
Merge pull request #3618 from chrisvest/2.2-no-native-mmap

Make the PageCache the only way to map files into memory.
Passes id iterable as ResourceIterable into IdMapper

since that needs to be closed after reading.
Correct a bit mask for collision marker for encoded strings

for the id mapper that encodes strings into longs in the batch importer.
This faulty bitmask was discovered when importing nodes with very long
string ids, therefore such a randomized test was added as well.