load.sh, install.sh: process parameters
default-template.mapnik: bugfix (#end all #for)
preprocess.pl: use env variables from load.sh, replace strings in mapnik file
load.sh, install.sh: Add help option
Rewrite compatibility; move old file to documentation of default base style
Compatibility: MapServer, GeoServer
README: adapt introduction
Default Style: support text-position: center / line