reduce the exceptions thrown by theme loader to ThemeException
theme: disable tourism=info
theme: add Newtron

- fix: VtmThemes enum
theme: slight orange primary roads
example: move theme menu to base
example: fix theme menu radio toggle
move TagFilter stuff to OsmTileLayer
refactor: TileLoader.createLoader()
get theme from VectorTileLayer, instead of setting it on Loader
docs: MatchingCacheKey
refactor: MapTile hold generic TileData - Testing
start TileLoaderHook:

- only create ExtrusionLayers when a BuildingLayer is attached
use Object as ID for TileData
docs: MapTile
PathLayer - inner class should be static
insert new hooks at front
move Text/Symbol handling to LabelTileLoaderHook
move Label/Symbol data from MapTile to LabelTileData
let TileLoaderHook stop further processing

- return false when no other loader hook should process
  the current element
add TileLoaderProcessHook to intercept MapElement processing