* Change the implementation of GetAll() in `preference_store.go` to return an
object from `model` and a *model.AppError.
Change the Interface in `store.go` to accomodate for the change
Change the test that called the GetAll() function
* Rename the result variable to preferences so it makes more sense.
Use assertions to keep the test consistent
* Generate the correct mocks after the code changes
* Remove redundant conditions
* Address govet errors
* Resolve conflicts with master's new changes
* Fix Save() function according to the new changes in master (Got
overwritten with the previous commit)
* Change the assertions to have the same format as commit 2d97f01
2e79ae9636