Eval: pass 'additional_code' to eval()
Process Mapnik: get canvas properties by calling eval functions

- closes #28
Func Match: remove obsolete code (dirty hack for canvas properties)
Merge branch 'branch-0.9' into standalone
Mode standalone: default no bbox -> whole database
DB/*: handle no bbox
DB/Osmosis: Bugfix, handle ways with <4 points

- ST_IsClosed does not work for ways with <4 points -> additional query
Mode standalone: geometry might be empty -> set to null
Mode Standalone: Group results for one object together

- add 'geometry' to a result if it differs from original geometry
- add 'pseudo_element' to each result
Mode Standalone: documentation (CHANGELOG, README)