Add extra newline between consecutive commands examples.

These 6 files had multiple examples all separated by a single newline.
While rendering it in markdown, the examples all come up in a single
line.
Adding another newline makes rendering better.
Also will help in easier copying (double click on the line to copy).

pages/common/cal.md

@@ -5,15 +5,19 @@
 - Display a calendar for the current month or specified month
 
 `cal`
+
 `cal -m {{12}}`
+
 `cal -m {{Dec}}`
 
 - Display a calendar for the current year or a specified year
 
 `cal -y`
+
 `cal 2013`
 
 - Display date of Easter (western churches)
 
 `ncal -e`
+
 `ncal -e 2013`