OPENDJ-1602 (CR-5566) New pluggable storage based backend

Reduced the number of compilation errors in package "org.opends.server.backends.pluggable".


*.java:
Passed in (Readable|Writeable)Storage objects rather than null in several method calls.
Removed more references to Berkeley JE classes.

TreeName.java:
Added replaceSuffix() and getIndex().

WriteableStorage.java:
Added truncateTree() and deleteTree().

EntryContainer.java:
Removed beginTransaction(), transactionCommit(), transactionAbort(),

RootContainer.java:
In preload(), removed the implementation as it is unsupported for now.

VerifyJob.java
VLVIndex.java