add isMobile/isDesktop segments #3157

Using some of the changes from #3133, we can add two new segments, isMobile & isDesktop. They would have to be views that are transformed into existing segments, ie, isMobile -> operatingSystem==ios,operatingSystem==psp,etc. . This isn't currently done and it may take some work to make it possible.

Could be done around:

Index: Segment.php
===================================================================
--- Segment.php (revision 6368)
+++ Segment.php (working copy)
@@ -104,6 +104,8 @@

             $sqlName = $segment['sqlSegment'];

+            // somewhere here we could read a 'viewSegment' and use this instead of a segment meaning a SQL field
+            
             // check permission
             if(isset($segment['permission'])
                 && $segment['permission'] != 1)

See: #3961

Let's add it to our Custom Segments examples