Support loading teams from server, add button to upload teams

[mia-pi-git]

Client-side integration for the teams database.
This PR:

• Adds a button to upload a team next to the pokepaste button.
• Supports pulling teams from the external DB via the loginserver. This is split into two levels: on startup, the client requests a list of teams from the loginserver, which responds with a list of teamIDs, mon IDs from that team, format, and team name. This leaves out the majority of the data. When the user opens the team in teambuilder, or tries to do anything with it, the app loads it from loginserver, caches it, then uses it.

I dislike having to add a callback parameter to sendTeam, but unfortunately we do not support async/await at the moment. Will take suggestions to improve that though.