Generating graphql mutations, list with optional arguments, query by pk

[rastislav-balcercik]

Improvements to #124

• Simplified output, all queries and fragments in one graphql query string
• Checking if query_root is type 'LIST'

[rastislav-balcercik]

WIP #111

Done:

• Query list, by pk
• Optinal arguments
• Building mutation queries

To do:

• returning (mutations)
• mutation type refactoring (I think it is not neccessary to check mutation args to find type)
• more testing

[rastislav-balcercik]

WIP #111, #122 generatePages now generates .graphql files with queries/mutations + fragments from introspection query and replaces useQuery placeholder in template for generated query