it is better to be able to create a json with layout content reading from DB

[jtydhr88]

In that latest DXP, Liferay has a new layout type called fragment or content.
Not like a widget/portlet layout, fragment layouts store the structure as json in DB.
In some cases, developers need to read the json and store in their custom module, so it is better to have a way to create a json with this content from DB.
Some initial ideas:

1. a menu item under File-> New to popup a window
2. a window shows available site/group list, along with available layout/page list
3. after choosing proper site and layout, it will read the content from DB basing on selected the information group and layout

Some key tables relating to this topic:

1. layout
2. layoutpagetemplatestructure
3. layoutpagetemplatestructurerel
4. fragmententrylink