Fix for slime/slime#144.  It turns out that there are 2 nicknames in use

And both are relatively common.  The ```swank-trace-dialog``` package had the nickname ```std``` (although never used the nickname, AFAICT), and in metering.lisp there was a ```monitor``` package that had the nickname ```mon```. The nickname was referenced in a  few places, which I've now changed. The last nickname has been around for a while, and is only used in CCL and CLISP.

For better or for worse, I've removed *both* nicknames and renamed the ```monitor``` package to ```swank-monitor```.

I probably should have stuck to just fixing the ```std``` nickname, but I agree with @attila-lendvai , we should be conservative with shared namespaces.