Fix yarp_completion detection of bash completion version

Fixes #126
Add end of line at the end of path.d/xxx.ini files
remove static SystemClock instance, fixes #129

Using a static instance here was lazy and relied on the assumption
that yarp::os::Time would only be used late, after library
initialization.  But existing code (e.g. yarpview) breaks that
assumption.  Thanks @gsaponaro for reporting.
fix Value assignment operator under reassignment, see #128

For v = v2, a pre-existing value in v of a different type to v2
could disrupt the copy.  Thanks @pattacini for reporting.
give a clearer message when a thread fails to start

fixes #127, thanks @JoErNanO!
Exit cleanly if playback with no cameras
Documentation fixes
Add info when playback finishing with no loop
Print resolution and fps info
Print openni and nite version info
Remove debug line