Remove text-force-odd-labels

mapnik/mapnik#2120 removed `force_odd_labels`, which may have never worked (according to comments in that issue).  When used with recent `mapnik-2.3` nightlies, Cascadenik fails with the following error:

```
Traceback (most recent call last):
  File "/usr/local/bin/cascadenik-compile.py", line 100, in <module>
    sys.exit(main(layersfile, outputfile, **options.__dict__))
  File "/usr/local/bin/cascadenik-compile.py", line 33, in main
    cascadenik.load_map(mmap, src_file, dirname(realpath(dest_file)), **load_kwargs)
  File "/usr/local/lib/python2.7/dist-packages/cascadenik/__init__.py", line 90, in load_map
    compile(src_file, dirs, verbose, datasources_cfg=datasources_cfg, user_styles=user_styles, scale=scale).to_mapnik(map, dirs)
  File "/usr/local/lib/python2.7/dist-packages/cascadenik/output.py", line 74, in to_mapnik
    sym = symbolizer.to_mapnik(fontsets)
  File "/usr/local/lib/python2.7/dist-packages/cascadenik/output.py", line 396, in to_mapnik
    sym.properties.force_odd_labels = self.force_odd_labels.value if self.force_odd_labels else sym.properties.force_odd_labels
AttributeError: 'TextSymbolizerProperties' object has no attribute 'force_odd_labels'
```