Feature/issue 2/multiple premises

[VoxBorealis]

Resolves #2
Resolves #74
Resolves #73

List of changes in this PR

DB:

• Create table for Offices
• Add defaultOffice (reference to Office) column to People table
• Add a reference to Offices in Signups and Defaultsignups
• Add a 'emoji' column to Offices?
• Add an office reference to Jobs

Front:

• Add an input modal for creating offices
• Add an input modal for modifying offices (update & delete)
• Add a view for when the app has zero offices added
• Add dropdown menu for office selection to app home tab or to the 'oletusasetukset' modal (rename to 'asetukset'?)
• Only show list of registrations for the selected office
• If a user has registered to another office for a particular day, communicate that to the in some way. (different colored buttons)
• Same thing with default signup modal

Backend:

• Modify all registration and default registration service getters to include an office parameter. (perhaps an optional parameter? If no arg, then return all registrations)
• Check all calls to the above mentioned functions to see if adding an office parameter is necessary.
• Add all necessary getters & setters for offices

Misc:

• Make necessary changes to scheduledMessage & laterRegistration
• REMOVED Update slash commands (/listaa, /ilmoita, /poista) to support multiple premises?
• Update docstring where necessary
• Remove unnecessary console.logs (even those unrelated to this issue, such as the cache logs)
• Remove outdated workaround related to Fix handling of disconnects in socket mode #73