add config to e2e server app

[tobiasKaminsky]

• add "restrict to hardware based token on desktop"
• this then should show e2e as disabled/remove entry in capability

[tobiasKaminsky]

@artonge @Altahrim

[artonge]

Could you be more explicit on the requirement ?

[susnux]

I guess this means there is a setting:

• force hardware based keys

Which then will force encryption to use a HSM instead of the server as the CA.
This then is communicated to the clients using capabilites.

If this is correct @tobiasKaminsky then this looks like:

• add new setting
• make setting available in capabilities
• disabled web ui support (webui cannot use PKS#11 because there is no way to communicate with devices)
• disable getServerKey and signPublicKey endpoints because this is now done by HSM.