Add decryption command line tool

We sometimes need to be able to view encrypted contents of the database.
This command line tools allows us to do this.

Usage:

> KEY=<encryption_key_here> node ~/ems_db/tools/decrpt.js
<encrypted_string>

scripts/decrypt.js

@@ -0,0 +1,10 @@
+const { decrypt }  = require('../helpers/encryption');
+
+
+(async () => {
+
+    const decrypted = await decrypt(process.argv[2]);
+    console.log(decrypted);
+
+})();
+