Add -[FMResultSet typeInformation] to mitigate missing type information in FMResultSet.

The FMResultSet API destroys column information in the database,
particularly in the float vs integer case. As a result, the
-[FMResultSet resultDictionary] API smashes both ints and floats
together as NSNumber*, making it difficult to introspect.

This API allows a minimal amount of introspection to work around
this problem.

In my case, I needed this API to deal with a fairly run-of-the-mill floating point formatting issue, since SQLite doesn't have actual decimal types.