Symlink indexer

Indexes a DirectoryContainer by creating symlinks to the Blob content files. These symlinks can then be accessed by 3rd party apps that just expect a filesystem API.

This indexer is intended to be replaced by some better filsystem abstraction layer.
Redone without using indexes

 - merge master
 - remove index changes
 - add Symlinker
Merge branch 'symlink-indexer'

Conflicts:
	src/doss/local/LocalBlobStore.java
	src/doss/local/LocalBlobTx.java
	test/doss/sql/SqlBlobIndexTest.java