ExtFunction introduced to generator
interface for external functions created
ext functions progress
progress
new ExtFunction implementation, synced with Hermes
Does not work. External functions generated, registered to WeakForm and used in forms.
Merge remote-tracking branch 'kus/master'

Conflicts:
	agros2d-generator/generator_module.cpp
	agros2d-generator/generator_module.h
	agros2d-library/hermes2d/module.cpp
	agros2d-library/hermes2d/plugin_interface.h
	hermes/hermes2d/src/function/postprocessing.cpp
	resources/templates/generator/coupling_interface_h.tpl
	resources/templates/generator/interface_cpp.tpl
	resources/templates/generator/interface_h.tpl
	resources/templates/generator/weakform_cpp.tpl