Port commands to use common setup code

Initialization logic needed for serve, build, and upload is now
much more clear than it was when these functions were written.

This commit refactors all of them to use a new common_setup
module for all of their initialization that's the same.

src/lib.rs

@@ -17,6 +17,7 @@ mod tree_view;
 
 mod auth_cookie;
 mod change_processor;
+mod common_setup;
 mod imfs;
 mod message_queue;
 mod multimap;