Add updated IDF & parameters for ALF instrument

Supplied by R. Ewings.

instrument/ALF_Definition_20130317-.xml

@@ -5,7 +5,7 @@
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://www.mantidproject.org/IDF/1.0 http://schema.mantidproject.org/IDF/1.0/IDFSchema.xsd"
  name="ALF" valid-from   ="2015-03-17 00:00:00"
-                        valid-to     ="2100-01-31 23:59:59"
+                        valid-to     ="2018-04-16 23:59:59"
 		        last-modified="2015-03-27 00:00:00">
  
    <defaults>

instrument/ALF_Parameters.xml

+<?xml version="1.0" encoding="UTF-8" ?>
+<parameter-file instrument = "ALF" valid-from = "1900-06-12T00:00:00">
+
+<component-link name = "ALF">
+
+<!-- files properties : -->
+
+<!-- Specify that the detector positions should be taken from the data file -->
+<parameter name="det-pos-source" type="string">
+  <value val="datafile"/>
+</parameter>
+<!-- The file which defines proper (calibrated) detector positions 
+     if None - it is undefined -->
+<parameter name="det_cal_file" type="string">
+   <value val="None"/>
+   <description is = "The file which defines proper (calibrated) detector positions.
+                      If property set to None - this file is undefined."/>
+</parameter>
+
+  <!-- -->
+</component-link>
+
+</parameter-file>