Move 'scan' to 'scan_rel', make Ctid a common data type

In preparation for producing a 'scan_page' that performs intra-page
fidelity checking.

Add a test to at least work as an example and test the testing system.
Support arguments to tox via ./t
Set executable bit on setup.py
Switch to distutils to setuptools
Add SQL quoting procedures
Begin adding intra-page scanning operators