Search Scope for dataset panel
DatasetPanel need a SearchScope vector to process search function. In
SearchScope object, it has namespace, config and endpoints. Currently, The
SearchScope object is instantialed in initSearchScope method in
TabbedLibraryPane class. In this method, configure file path was hard coded
there there and everything was read from configure file.
Eventually, kepler will read the info from both ecogrid registry and configure
file rather than configure file only for SearchScope. So we need an another
class, e.g. SearchScopeController, it will fingure out the info from both
registry nodes and configure file. We also need a way to figured out how to get
ConfigXML object convenientlly rather than passed it.