Fix TextArea's font

Using a Binding element overrides TextArea::font with a value from
TextAreaStyle::font, whereas the style is only supposed to provide
the default value. Use TextSingleton's font to avoid the original
binding loop.

Task-number: QTBUG-39328
Change-Id: I90113ef03dd31b2a060dfe12361708f99b35eb53
Reviewed-by: Liang Qi <liang.qi@digia.com>
Reviewed-by: Caroline Chao <caroline.chao@digia.com>
TextField::font: fix the default value handling

Assigning undefined to font is not possible, so use TextSingleton::font
as a fallback instead of undefined.

Change-Id: If148f7773ca784c0a1eb78f952dfad073fa9b1e3
Reviewed-by: Liang Qi <liang.qi@digia.com>
Reviewed-by: Caroline Chao <caroline.chao@digia.com>
TableViewColumn: Process all the rows in resizeToContents()

... including the first row.

Task-number: QTBUG-39337
Change-Id: I55bf61168840e9a7a5b31d7be2182b6974371a4a
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>
TableView: Reset dragged header position if not moved

The user expects the "ghost" header to be aligned with the actual
column header when he starts dragging it.

Change-Id: Ifccf633403a72fe8448132fe6c349a85acba28d7
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>
TableView: Make sure we get the content width with hidden header

The key is to get a headerRowDelegate of non-null dimensions.

Task-number: QTBUG-39393
Change-Id: I5ceadb07ebfc84142bbbfe98c5d61780e0314cf5
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>
Menu: Properly relay enabled state to QPA menu object

Task-number: QTBUG-39384
Change-Id: I1b71912b4f35ea0aa9e06667a5c0ecedec30f980
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>
TableView: Allow resizing and scrolling single-column tables

Also makes sure the resize handle is visible in desktop style.

Task-number: QTBUG-39393
Change-Id: I44410c65e76b0a3221ea5fce713c1f1b69079947
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>
Menu: Don't open disabled submenus

Task-number: QTBUG-39384
Change-Id: I5310c6efb0a7045f6f89c6347551a0043d8e0ca6
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>
Doc: Updated layouts docs with images and snippets

The images and the corresponding snippets
should help the reader understand the Quick Layouts
better.

Task-number: QTBUG-33799
Change-Id: I0a4831f33d99de87fcd7cb68a36844885509bb06
Sanity-Review: Qt Sanity Bot <qt_sanitybot@qt-project.org>
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>
Reviewed-by: Jan Arve Sæther <jan-arve.saether@digia.com>