This allows us to use UNIX filesystem permissions for access control.
Previously, any process in the network namespace could connect to it,
which is insecure for obvious reasons.
Verified that correct permissions are set:
```
# ls -lisa /run/bridge/
total 8
31996269 4 drwxrwxrwx 2 root root 4096 Nov 23 21:58 .
14676759 4 drwxr-xr-x 1 root root 4096 Nov 23 21:58 ..
31996306 0 srwx------ 1 root root 0 Nov 23 21:58 agent.sock
```
Fixes#119
* bridge: add secp check instruction
* solana: update to secp solana upstream
* solana: iteration on secp
* solana: fix secp instruction
serialization indices were off and secp ix data was serialized twice
* solana: optimize ix serialization
* agent: send multiple chunks of signatures
* doc: update protocol spec
* solana: store signatures in siginfo; reconstruct signed VAA in webinterface
* solana: reformat
* solana: add rustfmt config
Leopold Schabel
Hendrik Hofstadt
Hendrik Hofstadt