Added more logic gates and fixed placement issues

ui/assets/README.md

@@ -1,6 +1,5 @@
 Start/Stop icons taken from https://iconsmind.com/ (modified)
 
-Logic Gates taken from Wikimedia Commons. The authors are
-* jjbeard (AND, OR)
+Logic Gates taken from Wikimedia Commons. https://commons.wikimedia.org/wiki/Logic_gates_unified_symbols
 
 The Wikimedia icons are part of the public domain

ui/assets/resources.qrc

@@ -6,5 +6,10 @@
     <qresource prefix="/components">
         <file>and.png</file>
         <file>or.png</file>
+        <file>nand.png</file>
+        <file>nor.png</file>
+        <file>not.png</file>
+        <file>xnor.png</file>
+        <file>xor.png</file>
     </qresource>
 </RCC>