Merge pull request #490 from nodiscc/dev-1.0

Add the development wiki as a submodule
update italian translation
add mozmill test testPolicy/testIframeTree/testDefaultPolicies.js
rewrote readme.md a little
query interface when using aContext, fixes #503

aContext can be nsIDOMNode or nsIDOMWindow. Previously, it was assumed to be a DOM node, so it caused an error.
see https://developer.mozilla.org/en-US/docs/Mozilla/Tech/XPCOM/Reference/Interface/nsIContentPolicy#shouldLoad%28%29
Do not put placeholders for blacklisted images
Add preference for blacklist placeholders
do some changes to pull request #506. fixes #304.
revert mistakenly committed change
correct mozmill manifest.ini
[bugfix] automatically update subscriptions.html on changes (when opened)

subscriptions.html shows the subscriptions; depending on the default policy, different
list entries are displayed. So far the page has not been updated when the tab was open
and the default policy was changed in another tab. See also 576d09d
rename "tests/html/" directory to "tests/content/"
add 32px icons, fixes https://github.com/RequestPolicyContinued/requestpolicy/issues/450