Generic handling for multiple cmd-line modules.

Generic handling for multiple cmd-line modules.

Added generic methods for multiple independent modules within a single
command-line tool, and modified g_ana to use this.

By itself, does not change the external behavior significantly, but
makes it easier to implement parts of #666 and #672.
The wrapper binary in #685 should also be easy to implement using this
approach.

Change-Id: I3058bf5db2cbb7c7a1f9e4c87dd2db8f9727fe82