Simplify process of saving whole body joint configuration from yarpmotorgui

[traversaro]

While saving an whole body position, a form for each part appears. It would be more convenient to have to need to insert the position name in only one form.

Furthermore, when the file is saved a [ERROR]File saved and closed error message is printed, that should be converted to [INFO].

[randaz81]

Feature implemented by commit 7177114.
if user sets a file name in "Save all joints" dialog, the filename is propagated to all part sequences.
if user clicks on the cancel button, an individual dialog is opened for each part.