Adding empty files, based on the mysql backend
Adding empty classes as used
creation:sql_indexes_for_field (untested)
Creation now also adds a geometry-type constraint
Extremely hackish introspection.py

Instance data over type, parsing constraint strings, it's all there.
README updates (sql server limitations, todo)
Operations implemented (nothing else in operations.py)
Adding extended ops to TODO in README
get_distance implementation, lifted from spatialite
SQL Server doesn't implement STTransform

(Seriously)
Comment about why the ogc-table methods are unimplimented
Compiler module (don't think we need to override this)
Syntax errors and typos from actual testing!
Ignore .pyc files

(now that I'm actually running code)
geo_db_type needs to return the native db type

(which is always 'geometry', if you ignore geography support!  I didn't
understand what it was doing before)
Fixing autocomplete typo (mssql, not mysql)
Implementing the adapter + placeholder combo

(As is, this currently hits a bug in pyodbc itself as far as I can tell.
The adapter implements __str__, but the driver is rejecting it as an
invalid parameter.  Current hack is to wrap the call in fields.py with str())
Using a custom str-subclass adapter to work around pyodbc bug
Boilerplate compiler module

Each of these just mixin both the geo and driver compilers, but it turns
out that the compiler *name* can't be overridden, so we need to do this
in order to provide GeoSQLCompiler et al.
Implementing spatial lookup sql

This is now mostly functional I think.  Note, we also had to add the
conditional to the operations, since bits as returned by 'within' etc
aren't interpreted as booleans.