fix: HttpEngine tests
gwt: update UrlTileSource
add getter for split tilePath
LwHttp: prepare tilePath as byte[]
add missing headers
api: UrlTileSource:

- add UrlTileSource.getTileUrl(Tile) to create complete url string
- add TileUrlFormatter interface to override default formatter
- remove unused return from sendRequest()
Merge branch 'pluggable-network-layer'
cleanup: LwHttp
use debug log in IOUtils.closeQuietly