Ability to specify panel order in panel spec.
Update LICENSE File

Added Oliver Buchtala and Substance Software GmbH as core contributors.
OMerge branch 'master' of https://github.com/elifesciences/lens into lens_next
Include content panel.
Not needed to specify content panel in the panel order array.
Fix several regressions.
Merge branch 'lens_next' into reader_refactor

Conflicts:
	src/panel_factory.js
	src/panel_specification.js