fix a compil warning.
CvPcb: fix regressions :
Shows now a void field instead of the dummy footprint name $nonane (whenthere is no footprint selected in netlist).
The active footprint selection changes only if a new component is selected from the component file,
and does not change just when the next component is automatically selected, after a footprint selection.
Speed up delete association and auto associe.
* Factor test for auto save file into base frame class.
* Added auto save feature to Eeschema for saving schematics, addresses
launchpad question 173631.
* Add auto save interval control to Eeschema options dialog.
* Fix problem with subsequent auto saves in last commit.