Promote non-cluster variables that have cluster dependencies

[JamesWrigley]

If we have a context file like this:

@Variable(cluster=True)
def foo(run):
    return 42

@Variable
def bar(run):
    return 3.14

Then both jobs will execute locally first because bar is not a cluster variable and so it pulls in foo too when DAMNIT is executing bar. What we should do instead is promote bar to being a cluster variable like we do for proc variables:

DAMNIT/damnit/ctxsupport/ctxrunner.py

Line 52 in e2550d6

# Check for raw-data variables that depend on proc-data variables