[#5390] - Inconsistent ideas about Invalid ID characters

Using the UI to upload a resource various characters (space, minus...) are considered invalid in the ID of resources.

The UI rewrites these as underscores but this stops the resource from being found when the report is run.

When iReport uploads subreports along with the report it can happily create subreport resources with 'invalid' IDs and they run perfectly without having to adopt a horrendous underscore based naming scheme.