add fixture duplication script

[stevekm]

Created a script to help in producing new unique db fixtures based on old pre-existing ones.

Hopefully this will help with #139

[stevekm]

A note about this script: it is not possible to change the primary key on File entries, because there is a unique constraint in the File model on File.path.

This results in the problem described in #122. When loading a an old saved Run fixture set along with its new duplicated Run fixture set created with this script, the two Run's will have the exact same File entries due to the unique constraints in the database. Then, when trying to resolve the FileMetadata associated with each Port item in both the old and new fixture sets, only one FileMetadata will be returned because the current method for looking up FileMetadata for a given File requires returning only the Filemetadata with the highest version/most recent date.

Thus, despite having two unique Run's and sets of Port's and FileMetadata's, it is not possible to actually retrieve the FileMetadata for the newly created Port items due to the lack of direct association between Port and FileMetadata.

A potential solution could be to change the value for File.path, allowing for a new File primary key to be made and propagated, but currently it is not clear what value File.path could be changed to since Beagle assumes that all File.path items exist as real file paths on the filesystem. Need input on this.