Update sky_server:
- update its help string to admit that it wants the package path as well.
- be quiet by default, since it makes the build chatty.
- have a -v for verbose mode, for people who like it chatty.
- have a default port of 8000, since that's what everyone used.
- have a -p option to set the port, for people who don't use the default.
- remove its mapping for gen/, since a TODO told me to.
- remove the dependency on the build configuration, since it's no longer used.
- teach it about .dart files.
- rename sky_server/README to README.md, for consistency with other READMEs.
Update shelldb to speak the new sky_server protocol.
Update tests/services/iframe-embed-vmc.sky since the sky_server change broke the hack it was using.
Update skyserver.py to speak the new sky_server protocol.
Make webkitpy use SkyServer instead of spawning sky_server itself, since a TODO told me to.
Teach webkitpy about dart files.
Teach test_perf about dart files. (untested)
Teach sky_tool about main.dart, main.sky is deprecated. (untested)
R=eseidel@chromium.org
Review URL: https://codereview.chromium.org/1200993002.
