Doc: Edited configure options article.

-defined the build, install, and source directories.
-clarified some of the build type definitions.

Task-number: QTBUG-32766
Change-Id: I3ea557aa4487e8f14cfb820a0493915fcc6623cb
Reviewed-by: Mitch Curtis <mitch.curtis@digia.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Doc: Update Qt Enterprise information and supported platforms

Mention the availability of Qt Enterprise, Mobile Edition
on index page and whenever linking to open-source downloads
page on qt-project.org.

Also, update the following:
    - Reference platforms (OS X, Windows versions, mobile platforms)
    - Embedded platforms (Emb. Android, Qt Enterprise Embedded)
    - Divide Mobile platforms: Digia-supported & the rest
    - Mention other mobile platforms (Sailfish, Tizen, WinRT)

Task-number: QTBUG-33360
Change-Id: I36d74ca36699e24737b46af7a4a6f2736ada64af
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>
Reviewed-by: Sami Makkonen <sami.makkonen@digia.com>
Added changelog for 5.2.0 release

Task-number: QTBUG-33360
Change-Id: I29a5a21fe213bd7bfff3f4707de6c8142a74afcf
Reviewed-by: Sergio Ahumada <sergio.ahumada@digia.com>
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Doc: Fixed missing links in iOS, Android, WinCE, and Mac OS X pages.

-more attention is given to these pages for 5.2.0, so it is a good
 idea to make sure links work.

-WinCE page removed because it caused missing links.
 Pages do not link to it anyway.

Task-number: QTBUG-33360
Change-Id: I54b7ad874434feeef5670f15351ff522ebfec0b3
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>
Reviewed-by: Venugopal Shivashankar <venugopal.shivashankar@digia.com>
Merge remote-tracking branch 'origin/release' into stable

Change-Id: Ifa14612862e83036dfe130f60d9524d8f02ff0d2