OPENDJ-1602 New pluggable storage based backend

Index.java:
Extracted a method + moved it to VLVIndex.BufferedIndexValues.

VLVIndex.java:
Extracted a method + moved it to VLVIndex.BufferedVLVValues.
Extracted methods getVLVIndex(), isSortAttributeModified() (made the latter more efficient by exiting faster in from inner loop).
Used shouldInclude() throughout the class.
Code cleanup.

IndexBuffer.java:
Moved some methods to BufferedIndexValues and BufferedVLVValues.

git-svn-id: https://svn.forgerock.org/opendj/branches/opendj3-server-dev@11378 41b1ffd8-f28e-4786-ab96-9950f0a78031
Other code cleanups and extracted methods.

git-svn-id: https://svn.forgerock.org/opendj/branches/opendj3-server-dev@11380 41b1ffd8-f28e-4786-ab96-9950f0a78031