SOAP needs a lockfile

[Yoshanuikabundi]

Reproduction:

1. Run a SOAP alias in environment x
2. While 1 is running, change the environment spec for x
3. While 1 is running, run a second SOAP alias in environment x

Problem:

The second command deletes the environment (in order to update it) while the first command is running in it.

Solution:

Write a lock file for the environment being used when a command is executed. The file should contain the number of commands currently running in that environment. When a new command is run, create or increment the lock file. When a command finishes, decrement or delete the lock file. If a command is run that would update an environment withh a lockfile, exit with an error. Add an argument to run in the existing environment even if the spec has changed (eg, "--no-update")