Lock files for resources in use

[BeeFox-sys]

When opening profanity and logging into the same resource that you already have open in another instance of profanity causes unpredictable behavior, with no clear cause.

this can be highly confusing if a user doesn't realize this is the case, as it appears they are just regularly loosing connection.

after discussing this in the profanity room, an idea for a solution has been developed:

When using a resource, create a lock file for that resource.

if a user tries to connect to that resource, either via the connect command or autoconnect, profanity will notify the user that a lockfile exists:

Are you sure you want to connect to account foo?
It seems to be already connected with another profanity instance of pid <n>. This can also happen if profanity crashed.
To continue please enter y, to cancel the connection attempt enter any other key.

This allows the user to continue, in the case the lock file was left by a recent crash, or stop and open the forgotten instance of profanity.