Use traits Undefined for when name and units are undefined
BUG-FIX: Signal.unfold was messing up the axes attribures because it was not using AxesManager.remove method to remove the unfolder axes
Replace all .*_indexer with the new syntax
Add unfold test
Add Signal to signals
Rename hyperspy.components -> hyperspy._components and hyperspy.signals -> hyperspy._signals
EHN: fit with standard option in get_lines_intensity
Merge branch 'master' into edslab