Namespace util

Added a class to act as a namespace to make scoping easier, especially
assignment to outer variables in nested functions.
SignalWrapper cleanup

No longer plot automatically on init. This is now the responsibility of
the creator to call whenever the signal is clear. Also added the
workaround of re-emitting mainwindow's subWindowActivated after plotting
to make sure everything is in place when the event triggers (for the
second time).
Adapt to SignalWrapper cleanup + console numpy

Change add_signal_figure to reflect previous changes in SignalWrapper.
Also exec "import numpy as np" in console as numpy is frequently used
for console access.
Merge branch 'master' of https://github.com/vidartf/hyperspyUI