Add all backends at once
Add all backends at once

When no backends are loaded, a prompt pops up and
suggest to add some.

This patch adds the possibility to select all at once.

Signed-off-by: theo <4d1d9893eda835c5339560d5333cd14bbfaeb326@theocrite.org>
Signed-off-by: Romain Bignon <b8aabb4b95c817d9df69b6be95b2b94d6b1efe17@peerfuse.org>

frankrousseau/weboob,eirmag/weboob,yannrouillard/weboob,nojhan/weboob-devel,Boussadia/weboob,franek/weboob,willprice/weboob,Boussadia/weboob,nojhan/weboob-devel,laurent-george/weboob,Boussadia/weboob,frankrousseau/weboob,sputnick-dev/weboob,eirmag/weboob,Konubinix/weboob,Konubinix/weboob,RouxRC/weboob,yannrouillard/weboob,franek/weboob,sputnick-dev/weboob,willprice/weboob,sputnick-dev/weboob,Konubinix/weboob,laurent-george/weboob,yannrouillard/weboob,nojhan/weboob-devel,RouxRC/weboob,franek/weboob,Boussadia/weboob,eirmag/weboob,frankrousseau/weboob,RouxRC/weboob,laurent-george/weboob,willprice/weboob