Improve support for resource bundles and locales

[d-kozak]

Currently, the locale is fixed at image build time, i.e., registered resource bundles are only included for a single locale. This single locale is of course also the default locale at runtime. This should be made more flexible so that arbitrary locales can be included and the default locale is set correctly at run time.

[d-kozak]

The resource bundles can now be included in multiple locales, the list of included locales is customizable and the agent was modified to create configuration files accordingly.