User access roles are not collected recursively

[sveneberth]

viur-core/src/viur/core/modules/user.py

Lines 151 to 152 in c634c07

	# Go through all modules and evaluate available role-settings
	for name in dir(conf.main_app.vi):

This collects roles only from modules on first layer, but not on a second.

This cause problems in viur-shop and a customer project with nested modules.

Refers to viur-framework/viur-shop#58

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We need to find a better solution for the role names of nested modules as well. We need to agree this with vi-admin (/cc @akelch)