Moved JsEngine::Context into a private JsContext class
Got rid of v8.h dependency in JsValue.h
Made JsError a private class, no reason to have it in a public header
Get rid of v8.h dependency in JsEngine.h
Added helper class to store V8 values via auto_ptr
Added Android build target
Fixed: FileSystem;:Write should take an istream instance for input, not ostream