part implementation of photo category
new fields in photo class.
Now this fucking shit is compile.
Fixed error with string type parameter.
Added VkValueAttribute
Commit for merge.
Added VkApiMethod attribute and annotating methods from Photo category.
Made some improvements.
Simple unit-test url generation.
1. First implementation of unit test generator (very ugly)
2. Added Skip parameter
3. Added unit test category & tests for photos category.
Refactoring and some improvements.
All methods are skip.
Added some unit-tests for photo category.
Some fixes.
Merge branch 'photo_category'

Conflicts:
	VkNet/Utils/VkResponseToManualEnumCastsGenerator.cs
	VkNet/Utils/VkResponseToModelCastsGenerator.cs
	VkNet/Utils/VkResponseToSafetyEnumCastGenerator.cs
Fix errors after merge.