Transplant CSS from the main document to each iframe

We previously manually loaded CSS into these frames, which is flawed
because it completely bypasses ResourceLoader (so CSSJanus didn't flip
them, necessitating a bunch of hacks for RTL), and doesn't pull in
MediaWiki styles (so templates inside references don't render correctly).
Instead, this commit copies all styles from the main document into each
frame's document, inlining what it can.

Loading all styles in dialogs and inspectors caused some problems,
initially. We didn't namespace our styles for dialogs vs. inspectors
at all; the only reason inspector styles weren't being applied to dialogs
and vice versa was because we controlled which files were being loaded
in which context. This commit namespaces the inspector and dialog styles
where needed so they don't conflict and try to override each other.

Tested in Vector and Monobook, but not in Apex and not in RTL.

ve.init.mw.ViewPageTarget*.css:
* Namespace styles that are only intended for the main document
* Undo Monobook's font-size: x-small; in frames

*Dialog.js:
* Remove addLocalStylesheet() calls, we don't need those any more
** ve.ui.MWDialog seems to be unneeded now, we may want to remove it

*.css:
* Remove @noflip-ped RTL rules where they were just flipped versions of
  their LTR counterparts

ve.ui.Dialog.css, ve.ui.Inspector.css:
* Namespace styles with .ve-ui-dialog-content / .ve-ui-inspector-content

ve.ui.Frame.css:
* Move the margin:0 and padding:0 here (were in the frame <body>'s style
  attribute) and add background:none to prevent frames from getting
  the skin's background (grey in Vector, a book in Monobook)

ve.ui.Dialog.js, ve.ui.Inspector.js:
* Add ve-ui-dialog-content / ve-ui-inspector-content class to the
  frame's content <div> so we can restrict styles to only apply in
  dialogs / inspectors

ve.ui.Frame.js:
* Replace infrastructure for @import-ing stylesheets with transplantation
* Remove code polling to see when the stylesheets were loaded
** We can't do this in the new approach AFAIK, since all styles in the
   frame are either inlined or inaccessible due to the same-origin policy
** We also shouldn't need it because the browser should have cached the
   styles when it loaded the main document
* Apply ve-ui-frame-body class to the frame's <body> so we can style it
** Move inline padding:0;margin:0; into ve.ui.Frame.css
** Move the ve-ltr/ve-rtl class up to the <body>

ve.ui.Window.js:
* Remove infrastructure registering stylesheet URLs to load

Change-Id: I4a37115301811ad860f4578344a04873ea8c2b69