Implementation: Add billing rate support for projects

Implementation issue for #54 (closed). This is broken down into multiple smaller MRs:

• Implement team workspace. A team workspace is a panel to track billings for projects within that team. Each user can only belong to exactly one team - !19 (merged)
• Implement CRUD for services within teams. Each team provides a service to each client at a certain default rate. One team can provide multiple services - !20 (merged)
• Implement CRUD for projects within teams. Each team can have multiple projects. Most of the current project code are reusable. However, we should also allow syncing projects with Gitlab so that time records can be created using time records in Gitlab - !21 (merged)
• Implement CRUD for time records within teams. Each project has multiple time records tracked for it. These time records can be created manually or pulled from Gitlab - !22
• Implement CRUD for bill records and invoices. Bill records can be created from time records or manually. Multiple bill records can be grouped up into an invoice that will be sent to the client. - !23
• Build a manage tab (should be the first item) to manage all items - !24