Allow an MA to send a credential back.

If an MA has a speaks-for credential matching the authenticated user
and desired tool id, relay that credential back to the signing
tool. The signing tool, in turn, can relay that credential back to the
requesting tool. Pass the tool id to the MA via a URL parameter.
Add genilib.sendCredential

Allow an MA to send a credential back to the signing tool.
Permit a tool to specify an MA.

If a tool knows what MA the user should use to get their certificate,
pass that hint along to the signer tool. The signer tool will display
that MA as the default or append it to the list if it isn't in the set
of MAs.
Merge branch 'develop' into default-ma
Merge branch 'default-ma' into develop
Merge branch 'develop' into forward-sf-cred
Merge branch 'forward-sf-cred' into develop
Bump version to 0.5
Merge pull request #6 from tcmitchell/develop

Develop