"inertia on/off" and "detach [fullscreen]" commands.

and into partiview.cc, using new parti_add_commands hook.

Declare getfloats() (from partibrains.c at the moment).

but do return the Fl_Plot * so the caller can.

Increase MAXSTUFF yet again.

Can't actually do such rendering yet.

reports object name before invoking each command.

CONSTify input strings where possible.

``extern "C" { ... }'' doesn't need a post-semicolon.

Add parti_allobjs() for "gall" command.

Add parti_nudge_camera() to aid in tracking objects.

Lots of changes to support new time flow and additional
time-related GUI.  Probably not all there but at least somewhat usable.