Fix interface sort order

[barbieri]

In order to improve the generated code inter-dependencies, output in this order:

• Scalars (no dependencies)
• Enums (no dependencies)
• Input Objects (just depends on Scalars, Enums and other Input Objects)
• Interfaces (depends on Scalars, Enums, Input Objects and other objects)
• Objects (depend on all of above)
• Unions (depend on Objects)

Then sort by the previous rule considering interfaces of each.

Closes: #209 Closes: #189 Closes: #218

[coveralls]

Pull Request Test Coverage Report for Build 3622908549

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 2890398504:	0.0%
Covered Lines:	1553
Relevant Lines:	1553

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💛 - Coveralls