Moved older schemas to new folder, added a single DBWrench schema document, and added a read me file.

We have agreed to use GitHUB to version the schema document rather than
having separate files that we are all working on.  So, I copied the
0.83 schema file to a new file called “ODM2_DBWrench_Schema.xml”.  This
new file will be the master file that we merge future features into.
The readme file just describes what I did.