Implement static file serving for plugin.

Now Response accepts a File object to serve the file as a static file.
File system module's `read` method will return a File object and we can
pass the object to the Response constructor.
Implement standalone mode for test.

There is no need to launch zookeepr for test. And restarting zookeeper
server for every test makes test slow.

This patch implements the option to launch standalone mode. The
standalone mode will not make routing table so it doesn't need to launch
zookeeper.
Implement rhino source provider for assets.
Move javascript library code.

To add them in assets.
Seperate module source provider for library and plugin code.

Currently, both library and plugin uses UrlModuleSourceProvider. But
assets are packaged to jar on deployment and UrlModuleSourceProvider
cannot read source from jar. So this patch makes Beyond uses
AssetsModuleSourceProvider for library.
But plugin code still should read with UrlModuleSourceProvider.

To implement it this patch makes BeyondGlobal takes ModuleSourceProvider
as an argument. This provider will be used for library code.
Make BeyondJavaScriptEngine unsandboxed.

This patch turns off sandbox, because current AssetsModlueSourceProvider
doesn't support sandboxing.

It should be fixed ASAP.