DB/osm2pgsql: bugfix using mode standalone -> explicit type cast
DB: bugfix, return correct structure from objects_member_of()
DB/*: bugfix, return correct structure from objects_member_of()
DB/*::objects_near: bugfix, in mode standalone add additional type cast
DB/*::objects_near: do no longer include the current object
Examples: Update housenumbers example; recompile README
Bump to version 0.8.1; include links to stable/development version in README
Merge 'v0.8.1' into branch-0.9

Conflicts:
	CHANGELOG.creole
	README.md
	pgmapcss/version.py
Tagchecker: improve documentation
ol4pgm: initial support for ol4pgm https://github.com/plepe/ol4pgm