Variable length objects can be retrieved now

Conflicts:

	blaze/carray/carrayExtension.pyx
	blaze/persistence/blob.py
First version that can save variable length data.

Conflicts:

	blaze/carray/carrayExtension.pyx
	blaze/persistence/blob.py
Started a new branch for implementing a format for variable-length objects
Added a new fromiter() constructor.  Can use a Fixed shape or TypeVar (unknown length).

Conflicts:

	blaze/tests/test_quickstart.py
	blaze/toplevel.py
Merge branch 'vlen' into devel