sysdb: Don't pretty-print JSON in non-interactive mode. This is a work-around to fix integration tests (which expect the entire output on one line). A better solution will rely on configurable output formats. Also, disable interactive mode when using -c <cmd> options. It's not interactive after all :-)
store::memory: Add a plugin providing an in-memory store. This plugin replaces the default, built-in store. It is a simple wrapper around the built-in store implementation and, thus, provides exactly the same functionality but wrapped into a plugin.