Found and fixed a bug in ErrorHandler, canShowPerformanceIndicators.

It didn't work with CIDR format IP addresses.  I cannabilized the
code from canShowDebug and refactored it into its own method,
canShowBasedOnIP.  Both canShowDebug and canShowPerformanceIndicators call this.
Updated the docs for the debugIp setting to note that it's used for both
showDebug and showPerformanceIndicators.
Added about 20 more tests to ErrorHandler.t.  Only the two hard methods are
left, fatal (which closes the session at the end) and showDebug, which is
validating a ton of output.

docs/changelog/7.x.x.txt

@@ -4,6 +4,11 @@
  - fix: Bug in HttpProxy.pm
  - fix: Storage::Image copy does not create thumbnails
  - fix: Static export - redirect problems
+ - fixed a bug in Session::ErrorHandler::canShowPerformanceIndicators.  Moving
+   to CIDR format in debugIp broke it.  Added a new convenience method called
+   canShowBasedOnIP, which refactored out the identical code to share
+   between canShowDebug, canShowPerformanceIndicators and any other IP based
+   check for privileges.
 
 7.2.1
  - Made a change to version tag commits to deal with unusually long commit