Fix #443. Use CanTool for protection in E2 tool.

This means we always defer to prop protection addons for prop protection
decisions (as we should).
Use the global IsValid in E2 tool.

This is recommended practice because nil:IsValid() throws an error,
whereas IsValid(nil) returns false as it should.
Fix using the wrong tool name in E2 tool.
Remove useless checkbox from E2 editor.
Fix syntax and spelling errors.
Merge pull request #746 from wiremod/443-remote-updater-permissions

Fix #443. Use CanTool for protection in E2 tool.