Rename the various HTML DOM API Element sub-interfaces to not clash with real or future interfaces - scope them

[prushforth]

Currently none of the documented interfaces e.g. HTMLLinkElement has been exported as that name by the MapML.js module. However, they will be in future, and we have to ensure that they don't squat on current, or more likely, future HTMLElement interface names. So HTMLLinkElement (for example) will have to be renamed HTMLMapLinkElement to avoid a name collision with HTMLLinkElement, which actually exsists today.

[prushforth]

Note that when these are exported, they can be used, for example:

let foo = new MapML.HTMLMapLinkElement();
console.log(foo) // <map-link>