run_modal should not load the resource file itself

[Chimrod]

run_modal as an optional argument which allow to load the resource file. This is blocking if the application need to manage the resources by itself.

The argument should be an existing resource type and let the kind of source (file, string, hard-coded configuration) to the caller.

Some usage :

• to provide a default theme which could be overriden by the user
• no configuration application (everything would be hardcoded)