AutoRefactor'ed the pluggable and PDB backend

OPENDJ-2159 CR-7527 PDB Storage is read-only when using verify-index tool on Windows. The real problem is the server is killed before flushing has a chance to run and the fact operations for tree creation do not appear in the journal file. Adding a flag to open tree operations so that we can skip errors on missing trees while the storage is read only. Moreover, verify-index was trying to verify indexes already known to be in degraded state, and printing weird stats about them.

AutoRefactor'ed Use Diamond Operator

OPENDJ-1855 Reformat and cleanup pluggable backend code: adjust visibility, findbugs, ucdetector, etc... Fixed warnings reported by UCDetector

OPENDJ-1849 CR-6871 Remove references to JE from pluggable backend Additional decoupling of pluggable backend from JE. Class renames, comments and javadoc line up with new terminology, and general cleanup. Renamed classes: AbstractDatabaseContainer to AbstractTree DatabaseContainer to Tree DatabaseEnvironmentMonitor to BackendMonitor (given what the code does) DbPreloadComparator to TreePreloadComparator

OPENDJ-1849 CR-6835 Remove references to JE from pluggable backend Remove all cross references between pluggable and JE backends, in code and comments. Also refactor messages for all backend types, finally merging backend.properties with jeb.properties. JE specific messages are now in backend.properties, since there are not many of them now.

OPENDJ-1199: Reduce memory/disk usage of JE backend (variable length encoding for EntryIDSet)

OPENDJ-1849 Remove references to JE from pluggable backend Renamed JECompressedSchema to PersistentCompressedSchema