title: How do I safely add an attribute to an Opportunity?
body: <p>I am building a plugin that utilizes the new Business Process Flow in Dynamics 2013, and in order to take full advantage of the easy to use check-list style menu I have added two new attributes to the default Opportunity entity in Dynamics CRM.</p>
  
  <p>I have done this in the plugin's customizations.xml file by adding the attributes to the Opportunity Entity under the EntityInfo->Entity->Attributes section of the Entity xml.</p>
  
  <p>The addition of this field to the Opportunity works just as expected, though I am running into issues when uninstalling the plugin.</p>
  
  <p>Since this plugin will be widely available, I can't expect users to keep it on their systems forever.  </p>
  
  <p>On uninstallation of the plugin, however, Opportunities can no longer be viewed in the CRM 2013 Online.  When I try to view one I get the following:</p>
  
  <p><strong>Critical</strong></p>
  
  <p><strong>Query Builder Error</strong></p>
  
  <p><strong>The specified field does not exist in Microsoft Dynamics CRM</strong></p>
  
  <p>Is there something I can do within the customizations.xml file to ensure that once the plugin solution has been uninstalled, Dynamics CRM will no longer reference these fields?</p>
  
  <p>note:  This issue occurs on a brand new instance of Dynamics CRM 2013 (trial) with the plugin simply installed / uninstalled, so no other customizations are linking to changes from the plugin and causing the crash</p>