EHN: apply a function on signal
EHN: doc
EHN: User warning for scale/units difference
Merge branch 'master' into ENH_apply_function

Conflicts:
	hyperspy/signal.py
Merge branch 'apply_function' of https://github.com/pburdet/hyperspy into ENH_apply_function
Merge branch 'ENH_progress_bar' into ENH_apply_function
Merge branch 'master' into ENH_apply_function
Rename Signal.apply to Signal.apply_function, add support for non-vectorial
function and variable arguments, User Guide documentation and tests.
Merge pull request #2 from francisco-dlp/ENH_apply_function

Enh apply function
Merge branch 'master' into ENH_apply_function

Conflicts:
	hyperspy/signal.py
Fix broken merge