Extend WebFileLoader to leverage URL parameter parsing

The current set of URL parameter that we can use are as follow:
- application: Will override the default application name that is used
               in the HTML page which is used by the launcher.
- session: Allow the WebApplication to directly connect to an existing session
           by retreiving the connection information from it and connecting to it.
- file: The application will automatically request the loading of the file
        provided, relative to the --data-dir argument of the server.

Change-Id: Ib8a37fcdaee07e5e5f196704a742c06e009dd00b
Merge topic 'vtkweb-url-arg-parsing' into next

c5e5eb1 Extend WebFileLoader to leverage URL parameter parsing