fix #8849:
* Used scaled down (16x16 pixels) of large (.svg) images if no size is explicitely defined
* rendering of `emergency=aed` with recently added svg
* optimizations/refactoring in icons rotating/rescaling code
* fix of various warnings, javadoc

git-svn-id: http://josm.openstreetmap.de/svn/trunk@6172 0c6e7542-c601-0410-84e7-c038aed88b3b