DB support

[jtydhr88]

in some requirement, DB connection is needed, such as:

• add a liferay button to create DB quickly #204
• it is better to be able to create a json with layout content reading from DB  #205

it is better to support DB connection from low layer.
Actually, all information of DB connection is already provided in liferay workspace, and mysql library is provided by intellij layer or can be embedded by this plugin