Automate run of MedCAT service. Add integration test. Improve build performance

[alhendrickson]

Implemented two ways of running with automation, with no manual steps at runtime.

• Use the V1 model pack that is added to the image for testing. Pack was created by executing MedCAT v1 tutorial code on https://github.com/CogStack/MedCATtutorials/blob/5a07e4d77da404631cc16b47d3f1c6bd028de396/notebooks/introductory/Part_3_1_Building_a_Concept_Database_and_Vocabulary.ipynb
• Download a model pack during container startup, by setting env variables. This inverts the existing download then run, so it can now be run without manual steps

Next steps:

• Run the service internally using the terraform process