Document enhancement to call-blocking (#118)

* Document enhancement to call-blocking.

* Updated link to picture.

source/applications/call_block.rst

@@ -22,3 +22,9 @@ A list of numbers from which to block calls.
 .. image:: ../_static/images/fusionpbx_call_block.jpg
         :scale: 85%
 
+**Enhanced call-blocking introduced in Master branch 2.5.0:**
+Call-blocking does an exact match on the inbound caller-id number by default. 
+This behaviour can be changed to use SQL "like" comparison or regex based comparison by adding the following variable to the Default Settings:
+
+.. image:: ../_static/images/fusionpbx_call_block_matching.jpg
+        :scale: 85%