Add a __repr__ method to Model
Rename navigation/signal_indixer to inav/isign
The method that remove a signal axis now modify record_by accordingly
New MPL_HyperExplorer class that contains all that is common to MPL_HyperImage_Explorer and MPL_HyperSpectrum_Explorer
Merge branch 'master' of https://github.com/hyperspy/hyperspy
Merge branch 'master' into edslab