EventLoopGrid: print out pandaTaskID and improve nickname handling

This adds two features I've wanted in EventLoopGrid for a long time.

First, we print the pandaTaskID after task submission. It's a little extra output, but it's super handy, and already we had to point out in the tutorial that it's not printed out normally by EventLoopGrid, which is a little inconvenient.

Second, the handling of the nickname in output formatting. In the case that a proxy is not already available, the attempt to get the grid nickname fails and returns a long message (much more than 20 characters). A few moments later, prun asks for a password to create a grid proxy so that the job can be submitted - at which point getting the nickname succeeds. This prints a warning in case the nickname can't be found at submission time (can be resolved by doing a proxy init in advance). If the nickname can't be resolved, we leave "%nickname%" in place, and try to replace it in the python layer. This takes a little extra time for the submission step, because we effectively run prun three times instead of twice, but it means no crash in this condition, and the extra time is only taken in the case that you don't already have a proxy (ie the first time you submit a job).