fix dbf file import
Wrapper can now be used multiple times
Merge pull request #64 from nicolas-f/fix/dbfimport

Fix dbf file import, add unit test.

There were too many backticks. (TableLocation added them too.)
Merge pull request #63 from nicolas-f/fix/wrapper

Check connection and datasource before wrapping

Dev can now use SFSUtilities.wrapConnection without having to check if the connection is already wrapped.