Comment 18 for bug 1006414

Here's a patch to use JSON instead of pickle for the memcache client. Moving to SASL will still be something worth the effort after that, but that's a first step, I guess.

This needs some more serious testing, as I'm unsure I correctly checked that all users of memcache are using simple-enough object types.

Also, as I wasn't sure that getting unicode when loading strings from json was good, I wrapped things to get str instead. I'm assuming we really always care only about utf8 (not sure this is a correct assumption, though).