- while cnc supports multiple shells per auth client, the LaikaShell still only supports 1 concurrent shell at a time.
this feature is just preparing boilerplate for future features. shell treats all SHELL_* packets for the same shell, regardless of shellID
- can now open multiple shells per peer (change LAIKA_MAX_SHELLS)
- more sanity checking for public keys (new peers with duplicate keys are killed
- misc. refactoring, added cnc/cpeer.[ch]