* Update user.go
Added method to create user accounts using a privileged system_admin account
* Update user.go
Added respective method to handle the the APIv4 call to create users with privileged account(system_admin) by passing server restrictions of EnableUserCreation and/or EnableOpenServer set to false.
* Update user_test.go
Added test case
* Implement POST /users/search endpoint for APIv4
* PLT-2713 Added store functions for searching users that don't have a team
* PLT-2713 Added 'without_team' option when searching users
* PLT-2713 Added 'without_team' option when searching users (v4)
* Adding go vet to the api package
* Adding go vet to app package
* Adding go vet to manualtesting package
* Adding go vet to the model package
* Adding go vet to the store dir
* Adding go vet to utils package
* Adding missing dirs with go files
* Fixing up makefile
* Fixing up makefile
* Removing root dir
* added get user by username endpoint
* added get user by username unit test and driver
* changed username length to 22 characters max
* changed Params to UserName to Username
* reorganized get user by username and get user by email formatting in model/client4
* added get user by email endpoint for APIv4
* added get user by email endpoint unit test and driver
* removed the appended return of user ids on logout
* Added RequireEmail to validate user email. Also updated the get user by email endpoint and unit test
* Refactor and move session logic into app package
* Refactor email functions into the app package
* Refactor password update into app package
* Migrate user functions to app package
* Move team functions into app package
* Migrate channel functions into app package
* Pass SiteURL through to app functions
* Update based on feedback
* Add app package and move logic over from api package
* Change app package functions to return errors
* Move non-api tests into app package
* Fix merge
