Make the runtime configuration dialog non-modal. Fixes #5490

Major refactoring of the runtime code, Specifically:
  - Move the bulk of the core code from main() into a new Runtime class.
  - Break up the mass of code that was main() into a number of relatively simple functions.
  - Make the Configuration dialog synchronous so the Log dialog can be properly viewed.
  - Enable/disable menu options at the right time.
  - Remove support for Qt < 5.0.
  - Remove the application name constant and hardcode the name to simplify the code.
  - Improve log messages.
  - Replace the sdbm hashing with Qt's MD5 hashing.

runtime/FloatingWindow.ui

@@ -17,7 +17,7 @@
    </sizepolicy>
   </property>
   <property name="windowTitle">
-   <string>MainWindow</string>
+   <string>pgAdmin 4</string>
   </property>
   <widget class="QWidget" name="centralwidget">
    <widget class="QWidget" name="verticalLayoutWidget">