Improve the filter message and placement

This makes the text easier to translate (and more meaningful).
Also modifies its position to be centereed in order to look less "squeezed
into the corner".

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

qt-ui/filterwidget.ui

@@ -34,6 +34,19 @@
      <property name="spacing">
       <number>0</number>
      </property>
+     <item>
+      <spacer name="horizontalSpacer_2">
+       <property name="orientation">
+        <enum>Qt::Horizontal</enum>
+       </property>
+       <property name="sizeHint" stdset="0">
+        <size>
+         <width>40</width>
+         <height>20</height>
+        </size>
+       </property>
+      </spacer>
+     </item>
      <item>
       <widget class="QLabel" name="filterText">
        <property name="text">
@@ -112,7 +125,7 @@
         <x>0</x>
         <y>0</y>
         <width>594</width>
-        <height>332</height>
+        <height>337</height>
        </rect>
       </property>
      </widget>

qt-ui/simplewidgets.cpp

@@ -598,8 +598,7 @@ MultiFilter::MultiFilter(QWidget *parent) : QWidget(parent)
 
 void MultiFilter::filterFinished()
 {
-	ui->filterText->setText(tr("Dives filtered out: ") + QString::number(MultiFilterSortModel::instance()->divesFilteredOut)
-		+ tr("Dives being shown: ") + QString::number(MultiFilterSortModel::instance()->divesDisplayed));
+	ui->filterText->setText(tr("Filter shows %1 (of %2) dives").arg(MultiFilterSortModel::instance()->divesDisplayed).arg(dive_table.nr));
 }
 
 void MultiFilter::adjustHeight()