[linker] Fix routepolicy <-> webapp dependency

Make webapp depend on routepolicy (instead of the other way around), since webapp uses routepolicy code but routepolicy doesn't use webapp code.

Remove _routePolicy from __meteor_bootstrap__, as webapp is a package
now.

Simplify livedata.

Note that a future refactoring direction could be to push additional generic http server support code into routepolicy (and probably renaming it), while webapp becomes more specialized to serving the app HTML.