BFS btreeTest: fixed DEBUG build.

btreeTest: Revive test for BPlusTree implementation.

* Update pseudo cache with minimal set of block cache API.
* Update Inode, Journal and Volume stubs to current API.
* Add stubs for remaining VFS functions.
* Extend tests to also call BPlusTree::Validate() and bail on errors.
* Change duplicate tests to fill in the same value. While this isn't
strictly allowed, the tree validation can't work unless the values
match up.
* Lots of coding style cleanup, but much more should still be done...

The tests run through without errors.

BFS btreeTest: fixed DEBUG build.

btreeTest: Revive test for BPlusTree implementation.

* Update pseudo cache with minimal set of block cache API.
* Update Inode, Journal and Volume stubs to current API.
* Add stubs for remaining VFS functions.
* Extend tests to also call BPlusTree::Validate() and bail on errors.
* Change duplicate tests to fill in the same value. While this isn't
strictly allowed, the tree validation can't work unless the values
match up.
* Lots of coding style cleanup, but much more should still be done...

The tests run through without errors.