TASK Add flex attributes to StyleEntity / StyleDTO

[thejhh]

Add following attributes to SizeEntity / SizeDTO / Size and the SizeEntity.getCssStyles():

• display enum
• flexDirection enum
• flexWrap enum
• justify-content enum
• align-items enum
• align-content enum
• align-self enum
• flex-shrink number
• flex-grow number
• order number

See also:

• https://css-tricks.com/snippets/css/a-guide-to-flexbox/