Allow launch of L.Wrld.map directly onto an indoor map

[jonty-dawson]

Extend api to allow display of an indoor map without previously displaying an outdoor map.

Currently the best that can be achieved is something like:

var position = [51.515263,-0.075649];
var map = L.Wrld.map("map", <api_key>, {
    center: position,
    zoom: 18,
    indoorsEnabled: true
});

function onInitialStreamingComplete() {
    map.indoors.enter("EIM-aa6b833e-7bbd-48ae-a2ce-e39afe2e17c4");
}

function onIndoorMapEntered() {
    map.indoors.setFloor(8);
    map.setView(position, 21);
}

map.on("initialstreamingcomplete", onInitialStreamingComplete);
map.indoors.on("indoormapenter", onIndoorMapEntered);

To be released soon - watch this space!