Find/replace tool bar wasn't usable in very small width editors.

E.g. in split editors with small main window. We now have line edits
with a minimum size and use a flow layout for the replace buttons (which
will reduce width when necessary by laying out vertically).

Flow layout is taken from the Qt examples.

Task-number: QTCREATORBUG-3279
Change-Id: Ic07d4d3e75e3d928d6b53534adb42481ce26256b
Reviewed-on: http://codereview.qt.nokia.com/666


Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Leandro T. C. Melo <leandro.melo@nokia.com>