MAGETWO-43906: Long database prefix length breaks setup

- added prefix length rule description to tooltip

Author: Ivan Gavryshko

setup/view/magento/setup/add-database.phtml

@@ -335,7 +335,7 @@
             id="dbTablePrefix"
             class="form-el-input"
             tooltip-placement="right"
-            tooltip="Enter a prefix for database tables created in this installation. Use letters, numbers or underscores, and begin with a letter (Ex: ‘mg1_’)"
+            tooltip="Enter a prefix for database tables created in this installation. Use letters, numbers or underscores, and begin with a letter (Ex: ‘mg1_’). Table prefix length can't be more than 5 characters."
             tooltip-trigger="focus"
             tooltip-append-to-body="true"
             type="text"