allow supplying a database password for tests and migrations

Also make test/knexfile.js match mocha.start.js in terms of defaults for
environment variables.

Author: Mike Eldridge

mocha.start.js

@@ -25,6 +25,10 @@ if (DB_CLIENT === 'sqlite3') {
     user: process.env.DB_USER || 'root',
     database: process.env.DB_NAME || 'test'
   }
+
+  if (process.env.DB_PASS) {
+    connection.password = process.env.DB_PASS
+  }
 }
 
 JSDataAdapterTests.init({

test/knexfile.js

@@ -9,8 +9,12 @@ if (DB_CLIENT === 'sqlite3') {
 } else {
   connection = {
     host: process.env.DB_HOST || '127.0.0.1',
-    user: process.env.DB_USER,
-    database: process.env.DB_NAME
+    user: process.env.DB_USER || 'root',
+    database: process.env.DB_NAME || 'test'
+  }
+
+  if (process.env.DB_PASS) {
+    connection.password = process.env.DB_PASS
   }
 }