Application names used as keys but not sanitised

[modius]

Application names are used as a key for the cache but are not sanitised; this can raise the following ugly scenarios:

• application name with underscore borks the whole plugin; for example hello_myapp
• long application names are truncated; for example myyoubeautapplicationname gets shortened (ie there is a maximum key size)
• truncated names can lead to shared caches; for example if two long named apps share the same prefix

Suggest a config that allows developer to nominate the key they want for memcache. And default to a shortened version of app name with all underscores stripped out.