HTreeMapTest: add unlocking to prevent failing threads
DB: add shutdown code for collections to fix HTreeMap expiration threads closing
Add Delay Markers
Serializer: add Trusted interface. See #385
Remove locks disable option
Replace ASSERT with CC.PARANOID

assert() keyword does now eliminate assertion bytecode. That could prevent methods from JIT compilation and inlining
Eliminate markdown from Javadoc.

It have not worked on jdk 8, and general library such as MapDB hopes to be should have minimal dependencies.
Engine: rename a few constants, add javadoc
Engine: remove unused method for batch preallocation
Engine: enforce NPE if serializer is null
DBException: add first stub
Serializer: nosize serializers are not trusted
Fun.Pair: small fixes
SerializerPojo: add todo
Serializer: disable null handling on STRING and LONG
Engine: add unit tests for Engine null / delete / prealloc handling
StoreDirect: pass tests for handling null/prealloc/del values
StoreWal: pass most tests for handling null/prealloc/del values
StoreWal: pass all tests for handling null/prealloc/del values
Store: code reduction