- Enable sub-classing of hill shading algorithms, so users of the library can create theirs

- Get rid of the memory mapping of DEM files, use a simple and more efficient `BufferedInputStream` instead (`InputStream `in general, instead of the `ByteBuffer`)

- Create a new hill shading algorithm with better appearance and more customization

- chg: Update Guava and JTS dependencies

Co-authored-by: Jiří M. aka Menion <[email protected]>

…#1752)

Clarify behavior of 'v' attribute in Rendertheme documentation.

* Adding power-lines and power-poles to tag-mapping.xml

* Adapt zoom for power-lines and remove power-poles again

Elevation API - Get elevations of geographic points using offline digital elevation model data (DEM/SRTM).