Issue #6: Factor out the representation of credentials, which might not be specific to Repositories. For example a Proxy (#7) may require credentials. Retain getters on Repository for username and password until I fix CMR.
Issue #6: Factor out the representation of credentials, which might not be specific to Repositories.
For example a Proxy (#7) may require credentials. Retain getters on Repository
for username and password until I fix CMR.

jvasileff/ceylon-common,jvasileff/ceylon-common,ceylon/ceylon-common,ceylon/ceylon-common,jvasileff/ceylon-common,ceylon/ceylon-common