Add frequency file to be used as default

event_frequency.svlist

+DEL 100 500 0.2 0.2
+DEL 500 1000    0.2 0.4
+DEL 1000    2000    0.3 0.7
+DEL 2000    10000   0.2 0.9
+DEL 10000   50000   0.1 1.0 
+INV 100 500 0.2 0.2
+INV 500 1000    0.2 0.4
+INV 1000    2000    0.3 0.7
+INV 2000    10000   0.2 0.9
+INV 10000   50000   0.1 1.0
+DUP 100 500 0.2 0.2
+DUP 500 1000    0.2 0.4
+DUP 1000    2000    0.3 0.7
+DUP 2000    10000   0.2 0.9
+DUP 10000   50000   0.1 1.0