move leaflet client and rest servlet code into otp-core, update top level pom
remove otp-rest-servlet module. keep web.xml around for reference.

interestingly, message.properties was already duplicated in core.
remove various config files, some of which drifted in from a Go About branch
remove openlayers client, which is deprecated and will be moved to an external repo
remove otp-analyst module. it should be external or merged into the main leaflet client.

otp now has only a single maven-built submodule.
remove otp-datastore module. it is now a separate repo.
remove otp-gvsig module. it is now in a separate repo.
move all code out of otp-core into a single module. adapt maven and gradle builds.