client: take into account "selfPubKeyDir" from config when signing

http://camlistore.org/issue/210

Change-Id: Id6d75393a90bdf3141acc10fddc2b3cedee64422
jsonconfig: fix inconsistencies with booleans from environment variables

Use strconv.ParseBool.

Change-Id: Icbf27c78d9f144e333ba67063f4c1e32822fe9e8
Merge branch 'master' of https://camlistore.googlesource.com/camlistore