feat: move geostyler build to builder

[simonseyock]

This PR has some build optimizations that result in a way smaller image:

• It moves the geostyler build to the builder stage (the fully checked out repository was part of the image before, also git and maven are not needed in the runner image anymore)
• It removes most temporary file in the same stage they are created (removing the extracted geoserver jar probably has an impact)
• It runs apt purge in the same step that apt update and apt install are called

Also as ubuntu kinetic has gone end-of-life, I switched to mantic and a newer grass version

[simonseyock]

For anyone who is interested where the build size came from, here is a comparison between layer sizes for the most relevant lines: old

240MB wget -q -O /tmp/geoserver.zip http://downloads.sourceforge.net/project/geoserver/GeoServer/$GEOSERVER_VERSION/geoserver-$GEOSERVER_VERSION-war.zip &&     unzip geoserver.zip geoserver.war -d $CATALINA_HOME/webapps &&     mkdir -p $CATALINA_HOME/webapps/geoserver &&     unzip -q $CATALINA_HOME/webapps/geoserver.war -d $CATALINA_HOME/webapps/geoserver &&     rm $CATALINA_HOME/webapps/geoserver.war &&     mkdir -p $GEOSERVER_DATA_DIR # buildkit
0B mkdir -p ${GEOSERVER_LIB_DIR}tmp_extract # buildkit
6.01MB unzip -q ../gs-web-core-${GEOSERVER_VERSION}.jar # buildkit
30.4kB cat org/geoserver/web/css/minimalistic.css >> org/geoserver/web/css/geoserver.css # buildkit
4.81kB sed -i 's|</wicket:head>|<wicket:link><script type="text/javascript" src="js/modifications.js"></script></wicket:link></wicket:head>|g' org/geoserver/web/GeoServerBasePage.html # buildkit
2.24MB zip -qr9 ../gs-web-core-${GEOSERVER_VERSION}.jar * &&     cd .. &&     rm -rf tmp_extract # buildkit
722MB echo ${GEOSERVER_VERSION} > /tmp/version.txt; echo "2.15.6" >> /tmp/version.txt;     if (test $(sort -V /tmp/version.txt|head -n 1) != "2.15.6"); then         echo "Skipping installation of GeoStyler due to version incompatibility.";     else         echo "Building the GeoStyler extension now. This will take some time. Be patient!" ;         git clone --branch v1.0.0 https://github.com/geostyler/geostyler-geoserver-plugin.git ;         cd geostyler-geoserver-plugin ;         mvn -s "/tmp/settings.xml" -q -B -e -T 2C install ;         cp target/gs-geostyler-1.0.0.jar ${GEOSERVER_LIB_DIR}gs-geostyler-1.0.0.jar ;     fi # buildkit

new

136MB wget -q -O /geoserver-install/geoserver.zip http://downloads.sourceforge.net/project/geoserver/GeoServer/$GEOSERVER_VERSION/geoserver-$GEOSERVER_VERSION-war.zip &&     unzip geoserver.zip geoserver.war -d $CATALINA_HOME/webapps &&     mkdir -p $CATALINA_HOME/webapps/geoserver &&     unzip -q $CATALINA_HOME/webapps/geoserver.war -d $CATALINA_HOME/webapps/geoserver &&     rm $CATALINA_HOME/webapps/geoserver.war &&     mv /tmp/gs-geostyler-1.0.0.jar ${GEOSERVER_LIB_DIR}gs-geostyler-1.0.0.jar &&     mkdir -p $GEOSERVER_DATA_DIR &&     cd $GEOSERVER_LIB_DIR &&     mkdir tmp-extract &&     cd tmp-extract &&     unzip -q ../gs-web-core-${GEOSERVER_VERSION}.jar &&     mv /geoserver-install/minimalistic.css org/geoserver/web/css/minimalistic.css &&     cat org/geoserver/web/css/minimalistic.css >> org/geoserver/web/css/geoserver.css &&     mv /geoserver-install/modifications.js org/geoserver/web/js/modifications.js &&     sed -i 's|</wicket:head>|<wicket:link><script type="text/javascript" src="js/modifications.js"></script></wicket:link></wicket:head>|g' org/geoserver/web/GeoServerBasePage.html &&     zip -qr9 ../gs-web-core-${GEOSERVER_VERSION}.jar * &&     cd / &&     rm -rf geoserver-install # buildkit

The move of the geostyler build saved 722 MB and the removing of the downloaded geoserver jar in the same step saved another 100 MB