Importing of functions from another server module causes ImportError

[stefano.menci]

@stucork

any time you do anvil.server.call all server modules will be loaded,
since anvil doesn’t know ahead of time which functions are registered where.

Not only all the modules will be loaded, they will (most likely) be loaded in alphabetical order, and this may cause unexpected failures when you assume for example MainModule will be loaded first, while AnotherModule will be loaded first because it comes first in alphabetical order.