process type inherit from step

[eagmon]

Processes are just like steps but with an extra 'interval' key. So process type should inherit from step. Right now process type does not have 'address' or 'config':

process-bigraph/process_bigraph/type_system.py

Lines 147 to 157 in 6517fc8

	'process': {
	'_type': 'process',
	'_inherit': 'edge',
	'_apply': apply_process,
	'_serialize': serialize_process,
	'_deserialize': deserialize_process,
	'_check': check_process,
	'_divide': divide_process,
	'_description': '',
	# TODO: support reference to type parameters from other states
	'interval': 'interval',