(closes#3324)
Previously we allowed devs to swap out services that they didn't need.
This became difficult now that ES6 exports are immutable bindings.
But we can wrap the immutable bindings themselves in a live object,
to get back the flexibility that we used to have.
This change also drops the `taginfo` accessor on Context, since devs who want
to swap out taginfo service with something else can now do so through the live
binding. `iD.services.taginfo = myTaginfo()`
(closes#3377)
In most cases we prefer taginfo value results with lowercase letters.
A few OSM keys expect values to contain uppercase values
This is not an exhaustive list (e.g. `name` also has uppercase values)
but these are the fields where taginfo value lookup is most useful.
