Improve default size for several controls

We should set this to some decent default value that doesn't
look wrong. Note that the width and height definition in
TextArea could cause conflicts when used in layouts.

Change-Id: I815ff96c02f9a9a76c07d57181f3a24291c83c52
Reviewed-by: Jan Arve Sæther <jan-arve.saether@digia.com>
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>
Buttons: Allow overriding of visual properties when 'action' is set

Those properties are, text, tooltip, iconName, and iconSource.

Also, properly capitalized gallery's tooltips.

Change-Id: I1995a85565edd7aaa420279821d7c1a31ef18253
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>
Reviewed-by: Jens Bache-Wiig <jens.bache-wiig@digia.com>