Implement basic projects with revisions

[mickmister]

A Project will be tied to a channel, so if you are a member of the channel it belongs to, you have access to the project

Be able to browse projects you have access to
automatically searched by channel membership

need to have "view projects" button in channel header dropdown
or in the top header buttons

probably need to do zipping in frontend if doing zipping. but don't do zipping for now

need to be able to archive files in project
list files in channel that are not in project, in order to add to project

start with just backend stuff
create the data model
use slash commands
/files all - list all files in channel
/files - list files not attached to a project
/project add-file (file id) - assume one project per channel right now