Create a "model package" format

[nikmolnar]

Add support for creating and running model package files, which contain a model file and the data necessary to run it.

This could be as simple as a ZIP archive. Creating the package would involve searing the model for data dependencies, changing paths to be relative rather than absolute, and creating an archive with the modified model and dependent data.

Example archive structure:

model.mptz/
├─ model.mpt
├─ data/
   ├─ input.csv