Cleaning up comments

- Blobs are really inefficient in MySQL so should provide an option for end users to take into account the size of data stored
- varchars can be indexed for keys
- Values (which can be large) don't need to be indexed for any dbType; 
- optimized.valueSize is used because varchars are stored in the row inside InnoDB; Blobs are stored with a pointer and are glacial at scale.  A MySQL row has a total size limit of 64KB across all columns.