Assigns default memory size for relationship group store

The default size is 10M (or 0.03% size of nodestore if the size is allocated by AutoConfig)
Tagging for version 2.1.6
Updated auth docs for defaulting to enabled together with some more structure.
Back to development version.
2.1.6-SNAPSHOT -> 2.1.7-SNAPSHOT
Improves some messages concerning the state of store files

Some exception messages and debug logging statements were too generic
 and lacked information about the specific condition that could lead
 to the problem observed. This commit adds some information that can
 provide some insights that can be useful for debugging.
Add some unit tests for some of the property deduplication stuff in store migration
Adds a test for deleting node in auto index
Merge pull request #3551 from S124568/2.2-add-node-deleting-test-node-auto-index

Adds a test for deleting node in auto index
Less confusing docs for terminating transactions.
Merge pull request #3550 from chrisvest/2.2-moar-migration-tests

Add unit tests for some of the property deduplication stuff in store migration
Merge pull request #3539 from digitalstain/master

Improves some messages concerning the state of store files
Change auth to on by default
Cleanup user serialization format a bit
Merge pull request #3552 from nawroth/terminate

Less confusing docs for terminating transactions.
Merge pull request #3519 from jakewins/2.2-authon

Auth on by default
Merge pull request #3532 from nawroth/auth

Updated auth docs for defaulting to enabled
Merge pull request #3493 from S124568/2.1-add-MMIO-setting-relgroupstore

Assigns default memory size for relationship group store
Merge branch '2.1-maint'
Merge pull request #3557 from digitalstain/master

Null merge of 2.1-maint into master