add apps command doc #42

docs/appbase/apps.md

+# apps
+
+`apps` command gives detailed information on the user apps. 
+It includes the following additional stats.
+
+1. Number of API calls in the month
+2. Total number of records
+3. Storage size
+
+```sh
+> abc apps
+
++------+----------------+-----------+---------+---------+
+|  ID  |      NAME      | API CALLS | RECORDS | STORAGE |
++------+----------------+-----------+---------+---------+
+| 2442 | appname        |        42 |      42 |    4242 |
+| 2484 | another        |        84 |      84 |    8484 |
+| .... | .........      |       ... |     ... |     ... |
++------+----------------+-----------+---------+---------+
+```