[rfc][icedtea-web] allow permissions on the fly

[Jiri Vanek]

It is quite hard to preset all policies *before* run in sandbox is clicked.
On devconf, where this approach was quite appreciated, following idea was raised:
  - when mode is "run in sandbox"  AccessControlException access denied -permission.type- should be 
thrown, then instead throw, allow user to temprary/pernamently allow this policy for codebase.

During first run many of thsoe dialogs will rise, but at the end  the application will be well tuned.

AFAIk there is issue - the policy file can remember only allowed policies, but in this case we need 
to have also permanently banned policies saved. As policy file do not allow this, i see two solutions:
  - extend policy file - probably no way
  - have two "run in sanbox" buttons (or similar setting)
    - run in sandbox
    - interactive run in sandbox


Thoughts?

(no patch here!-)

J.