pan-control: fix css; refactor
pan-control: fix css; refactor

* add css to align other leaflet controls with the pan control
* add changeable pan control `options` to plugin namespace
* 'prevent Pancontrol from being activated by default' is not needed for current version
* fix try/catch block
* simplify plugin structure

3ch01c/ingress-intel-total-conversion,McBen/ingress-intel-total-conversion,sndirsch/ingress-intel-total-conversion,McBen/ingress-intel-total-conversion,McBen/ingress-intel-total-conversion,McBen/ingress-intel-total-conversion,McBen/ingress-intel-total-conversion,sndirsch/ingress-intel-total-conversion,3ch01c/ingress-intel-total-conversion,3ch01c/ingress-intel-total-conversion,3ch01c/ingress-intel-total-conversion,sndirsch/ingress-intel-total-conversion,3ch01c/ingress-intel-total-conversion,3ch01c/ingress-intel-total-conversion,sndirsch/ingress-intel-total-conversion,sndirsch/ingress-intel-total-conversion