(bug 40448) Replace legacy mwsuggest with mediawiki.searchSuggest

The module has been broken for a while now, but nobody noticed
because in plain core it is disabled by default, and in the
bundle we ship with Extension:Vector (and its SimpleSearch).

This commit removed the mediawiki.legacy.mwsuggest module (and
related components that become obsolete with its deletion) and
replaces it with the new mediawiki.searchSuggest module, which is
based on SimpleSearch from Extension:Vector (where it will be
removed soon).

The following and all references to it in core have been removed,
I also made sure that they weren't used in any of extensions/*.
Only matches in extensions/Settings and some file that dumped the startup module, and in extensions/Vector which are addressed in
I1d5bf81a8a0266c51c99d41eefacc0f4b3ae4b76.

Had to make a few updates to jquery.suggestions to make it work
in other skins. So far it was only used in Vector, but now that
it is used in mediawiki.searchSuggest, I noticed several issues
in other skins. Most importantly the fact that it assumed the
default offset was from the right corner, which isn't the case in
Monobook where the search bar is on the left (in the sidebar).

It now detects the appropiate origin corner automatically, and
also takes directionality of the page into account.

It also uses the correct font-size automatically. Previously it
used font-size: 0.8; but that only works in Vector. Every skin
seems to have its own way of making a sane font-size. In Monobook
the <body> has an extra small font-size which is then fixed in
div#globalWrapper, and in Vector it is extra large, which is then
fixed as well deeper in the document. Either way, the size on
<body> can't be used, and since this suggestions box is appended
to the <body> (it is a generic jQuery plugin without knowledge of
the document, and even if we could give it knowledge inside
the configuration, it'd have to be per-skin). So I removed the
Vector specific font-size and let it handle it automatically.
This was needed because it is now used in all skins.

Removed modules:
* mediawiki.legacy.mwsuggest:
  > Replaced with mediawiki.searchSuggest.

Removed messages:
* search-mwsuggest-enabled
* search-mwsuggest-disabled
  > No longer used.

Removed mw.config.values:
* wgMWSuggestTemplate
  > Obsolete.

* wgSearchNamespaces
  > Obsolete.

Removed server-side settings:
* $wgEnableMWSuggest
  > Suggestions are now enabled by default and can be disabled
    through the user preference `disablesuggest` still.
    They can be disabled by default site-wide or hidden from
    prefs through the standard mechanisms for that.

* $wgMWSuggestTemplate
  > Obsolete.

Removed methods
* SearchEngine::getMWSuggestTemplate()
  > Obsolete.

Filters:
 $ ack mwsuggest -i -Q --ignore-dir=languages/messages
 $ ack wgSearchNamespaces -Q

Message changes:
* vector-simplesearch-preference
  > It was wrong, it didn't activate search suggestions, that
    was handled by the Vector extension. This preference in
    MediaWiki core controls whether the SimpleSearch bar HTML
    and CSS will be used (e.g. the rectangle search box with
    the magnifying class instead of the browser-default input
    field with the plain submit buttons).

* searchsuggest-search
* searchsuggest-containing
  These come from Extension:Vector message and should be imported
  by translatewiki:
  - vector-simplesearch-search
  - vector-simplesearch-containing

Change-Id: Icd721011b40bb8d2c20aefa8b359a3e45413a07f
Sync stand-alone release notes changes

Change-Id: Ic07c57c4b3fb27074ea8a0d85b56837f8db81bd1