utils.py: add function plot_same_navigation

Can plot several spectra which all share the same axes_manager.
Making it possible to change the navigational position of all the plots
at the same time.
BUG-FIX: utils.plot_same_navigation had wrong variable name
utils.plot_same_navigation: improve docstring
Modify plot_same_navigation: add navigation parameter, rename function

Add navigation parameter which is passed to the individual plot
functions.
Renamed function to plot_sync_navigation
plot_sync_navigation moved from utils.py to drawing/utils.py
Merge branch 'master' into plot_same_navigation

Conflicts:
	hyperspy/drawing/utils.py
	hyperspy/utils.py
utils/plot.py: add drawing/utils.plot_sync_navigation to import
utils.plot.plot_sync_navigation: add preliminary docs in user guide
Change plot_sync_navigation to plot_signals

Add argument sync, which if set True will let all the signals share
the same navigation positions. If set False all the signals will
have seperate navigation positions.
Change documentation to plot_signals (instead of plot_sync_navigation)
Fix typo in plot_signals documentation
Added chi-squared and reduced chi-squared to model class. They are both signals at the moment, so could be slow.
Also added option to make progress bar for as_signal() optional.
fixed missing reference to data of chisq
will have to redo, removed additional changes to be moved to other branches
Merge branch 'master' into plot_signals

Conflicts:
	doc/user_guide/visualisation.rst
fixed array initialisations in model.py
fixed array initialisations in component.pt
Merge pull request #155 from to266/quicker_array_initialisation

Quicker array initialisation
Modify drawing.utils.plot_signals: add slider argument, navigation_list

navigation_list argument makes it possible to specify different
navigators for the different signals.
user_guide.visualization: Remove residual after using mergetool