Employees page

[shoumaw]

Similar to the existing customers page, implement an employees page with details & create screens.
Previously cases were using the users table to refer to employees but now we have a separate employees table.

Plus other changes:

1. Case.assignedTo should reference an Employee
2. Case.createdBy should reference an Employee (Current employee when creating a case should be Alex Morgan, probably hard-coded)
3. Remove the Case.updatedBy field