Add special logic to the MemoryDeviceDbContext to handle listing devices by account using the generic list function. This allows for the simplification of the GetValue method, and for the arguments to be passed from the repository in a manner more similar to how the devices would be retrieved from a database.
Add initial tests for update device.
Implement memory db context and device repository logic for the two update tests.
Test that update excepts if the device does not exist.
Refactor delete method to use the get method to retrieve a single instance. All attempts at retrieving a single instance should use the get method for consistency.