[BUGFIX] the class gm-style overwrites default styles for popup
[BUGFIX] the class gm-style overwrites default styles for popup

When the map included a Google Maps layer, the class gm-style is added to the
 map body. This class overwrite the default font styles for popups.

Fixes #127

3liz/lizmap-web-client,makinacorpus/lizmap-web-client,jancelin/lizmap-web-client,rldhont/lizmap-web-client,makinacorpus/lizmap-web-client,jancelin/lizmap-web-client,aeag/lizmap-web-client,3liz/lizmap-web-client,laurentj/lizmap-web-client,jancelin/lizmap-web-client,jancelin/lizmap-web-client,makinacorpus/lizmap-web-client,laurentj/lizmap-web-client,nboisteault/lizmap-web-client,3liz/lizmap-web-client,laurentj/lizmap-web-client,jancelin/lizmap-web-client,aeag/lizmap-web-client,aeag/lizmap-web-client,laurentj/lizmap-web-client,3liz/lizmap-web-client,rldhont/lizmap-web-client,aeag/lizmap-web-client,makinacorpus/lizmap-web-client,nboisteault/lizmap-web-client,nboisteault/lizmap-web-client,rldhont/lizmap-web-client,rldhont/lizmap-web-client,aeag/lizmap-web-client,makinacorpus/lizmap-web-client,nboisteault/lizmap-web-client,jancelin/lizmap-web-client