implement and hide traits compatibilty code so plugins do not have to
fview_fmf_replay: add next frame button
provide some more exported widgets to plugins
consolodate fview conditional features

* try to perform non-fatal imports (ros, wxvideoopengl) all
  in the same place and pass success of failure of these
  initilizations to plugins.
* init ROS once, early in fview
* remove some global state (wx does call __init__), no need
  to make stuff global to see it in OnInit
fix ros-free import logic
move some often copied code to fview.utils
import on_trait_change
show the log file path in error cases
print the camiface library details