Implement user nlog configs, update updater to ignore user config. Resolves #309

Also changes FilesystemManager to use system temp directory when appropriate. (reduces clutter on disk)

NLog.config

@@ -4,6 +4,8 @@
   <variable name="logStamp" value="${time} ${pad:padding=-8:inner=[${level:uppercase=true}]}" />
   <variable name="logContent" value="${message:withException=true}"/>
 
+  <include file="NLog-user.config"/>
+  
   <targets async="true">
     <target xsi:type="Null" name="null" formatMessage="false"  />
     <target xsi:type="File" name="keen" layout="${var:logStamp} ${logger}: ${var:logContent}" fileName="Logs\Keen-${shortdate}.log" />
@@ -15,6 +17,7 @@
   </targets>
 
   <rules>
+    <!-- Do not define custom rules here. Use NLog-user.config -->
     <logger name="Keen" minlevel="Warn" writeTo="main"/>
     <logger name="Keen" minlevel="Info" writeTo="console, wpf"/>
     <logger name="Keen" minlevel="Debug" writeTo="keen" final="true" />