enable piv-authenticator for alpha releases

[daringer]

• include piv-authenticator for alpha releases Bump opcard and add piv to alpha #233
• provide storage option to set data persistance to external memory Make storage configurable piv-authenticator#8

[sosthene-nitrokey]

Additionnal steps:

• Add rsa-backend (I think we should also merge the migration for opcard once we do that)
• Increase the size of trussed files Increase size of file writing trussed-dev/trussed#78, so that we can support certificate that are large enough to be actually useful
• Use streaming API for large certificates Implement large file streaming for certificates and other data objects piv-authenticator#12