Adjusted conference dialog for Qt5

resources/conference_dialog.ui

 <?xml version="1.0" encoding="UTF-8"?>
 <ui version="4.0">
- <class>ConferenceDialog</class>
- <widget class="QDialog" name="ConferenceDialog">
+ <class>conference_dialog</class>
+ <widget class="QDialog" name="conference_dialog">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
-    <width>305</width>
-    <height>125</height>
+    <width>330</width>
+    <height>150</height>
    </rect>
   </property>
   <property name="minimumSize">
    <size>
-    <width>305</width>
-    <height>125</height>
+    <width>330</width>
+    <height>150</height>
    </size>
   </property>
   <property name="windowTitle">
@@ -170,7 +170,7 @@
   <connection>
    <sender>accept_button</sender>
    <signal>clicked()</signal>
-   <receiver>ConferenceDialog</receiver>
+   <receiver>conference_dialog</receiver>
    <slot>accept()</slot>
    <hints>
     <hint type="sourcelabel">
@@ -186,7 +186,7 @@
   <connection>
    <sender>reject_button</sender>
    <signal>clicked()</signal>
-   <receiver>ConferenceDialog</receiver>
+   <receiver>conference_dialog</receiver>
    <slot>reject()</slot>
    <hints>
     <hint type="sourcelabel">