Change AppDF format

[akarimova]

Make the following elements/attrs not mandatory

description/texts/keywords
description/texts/short-description
description/texts/features
content-description/content-descriptors
content-description/included-activities
testing-instructions
consent
customer-support/phone
customer-support/website

Reduce required screenshot count from 4 to 2.

[akarimova]

remove type-storespecific element

[akarimova]

remove type-requirements-supportedresolutions

[akarimova]

remove type-requirements?