Get app info related to blind signatures from the signing node (or the app registry), not another node

[adamstallard]

Currently, we get information that the BrightID mobile reference app uses to determine when to update blind signatures (such as verification expiration length or verifications) from any node (which should have gotten it from the app registry), but these nodes could be out-of-sync--if their updater has crashed--and have different info than the node doing the signing, causing the client to think a verification is expired when it isn't, and linking to fail.

To avoid inconsistencies, the information could be retrieved from the node that will do the signing instead of the node the user is "connected" to.

@abramsymons opinion is that these should be retrieved from the app registry directly instead of through a node at all, but if we are going to use a node, it should be the same one that does the signing to avoid inconsistencies.