Fixing package offset

Due to casting to too specific type, IMember.
The source range is available on the ISourceReference.
Fixes package renaming

Need to rename the associated Package fragment, not the declaration.
Adding preferences for single letter
Fixes default reset
Fixes spelling in preference constants
Completing Ignore Single Letter

 * Change to preferences - removes extra default requirement
 * Removes unused Configuration
 * Fixes creation of dictionaries