tools: print "pad-added", "pad-removed" and "no-more-pads" signals for elements with sometimes pads
tools: print "pad-added", "pad-removed" and "no-more-pads" signals for elements with sometimes pads

It's often not obvious to people that elements like e.g. uridecodebin
(or demuxers) automatically support the standard signals of the
GstElement class, so let's print the useful pad-related ones for
elements with sometimes pads.

Lachann/gstreamer,krieger-od/gstreamer,collects/gstreamer,cablelabs/gstreamer,lubosz/gstreamer,Lachann/gstreamer,lovebug356/gstreamer,magcius/gstreamer,drothlis/gstreamer,surround-io/gstreamer,mparis/gstreamer,ahmedammar/platform_external_gst_gstreamer,drothlis/gstreamer,centricular/gstreamer,drothlis/gstreamer,ylatuya/gstreamer,Distrotech/gstreamer,lubosz/gstreamer,cfoch/gstreamer,ylatuya/gstreamer,ensonic/gstreamer,justinjoy/gstreamer,magcius/gstreamer,cfoch/gstreamer,Distrotech/gstreamer,shelsonjava/gstreamer,surround-io/gstreamer,justinjoy/gstreamer,centricular/gstreamer,mparis/gstreamer,jpxiong/gstreamer,lubosz/gstreamer,centricular/gstreamer,StreamUtils/gstreamer,jpakkane/gstreamer,surround-io/gstreamer,shelsonjava/gstreamer,krieger-od/gstreamer,krichter722/gstreamer,krichter722/gstreamer,jpxiong/gstreamer,krieger-od/gstreamer,ahmedammar/platform_external_gst_gstreamer,centricular/gstreamer,jpxiong/gstreamer,ensonic/gstreamer,drothlis/gstreamer,ylatuya/gstreamer,StreamUtils/gstreamer,cablelabs/gstreamer,cablelabs/gstreamer,krieger-od/gstreamer,jpakkane/gstreamer,collects/gstreamer,collects/gstreamer,krichter722/gstreamer,lovebug356/gstreamer,lovebug356/gstreamer,shelsonjava/gstreamer,ahmedammar/platform_external_gst_gstreamer,jpxiong/gstreamer,ylatuya/gstreamer,jpakkane/gstreamer,magcius/gstreamer,krichter722/gstreamer,ylatuya/gstreamer,cfoch/gstreamer,mparis/gstreamer,cfoch/gstreamer,Distrotech/gstreamer,cfoch/gstreamer,surround-io/gstreamer,shelsonjava/gstreamer,shelsonjava/gstreamer,cablelabs/gstreamer,Lachann/gstreamer,ensonic/gstreamer,magcius/gstreamer,jpakkane/gstreamer,lovebug356/gstreamer,Distrotech/gstreamer,lubosz/gstreamer,lovebug356/gstreamer,ahmedammar/platform_external_gst_gstreamer,jpakkane/gstreamer,Distrotech/gstreamer,magcius/gstreamer,ahmedammar/platform_external_gst_gstreamer,krieger-od/gstreamer,centricular/gstreamer,ensonic/gstreamer,justinjoy/gstreamer,jpxiong/gstreamer,surround-io/gstreamer,drothlis/gstreamer,collects/gstreamer,justinjoy/gstreamer,krichter722/gstreamer,StreamUtils/gstreamer,lubosz/gstreamer,Lachann/gstreamer,Lachann/gstreamer,mparis/gstreamer,collects/gstreamer,mparis/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,justinjoy/gstreamer,ensonic/gstreamer,cablelabs/gstreamer