Renamed io module to hio

Rename hyperspy.io to hyperspy.hio, to not have the same name as a
stdlib.
Option for modal interactive dialogs

Added options for interactive GUI tools to be modal, allowing e.g. for
scripting general routines.
Created Gaussian Model, which fits N gaussians

Implemented a Model that tries to fit N Gaussian components to a 1D
signal. N can also be auto-determined.
Added creation code for gaussian model +bugfix