Scalar description, improvements in addon types

• Scalar descriptions are printed
• Changed addon types description
• Replaced date format

Added Addon types

Merge pull request #46 from Maxofil/addon-types

added addon types + tests for addons

Added printing of directive arguments

v0.17.3

added printing of directive arguments

Bugfixes

• fixed obsolete condition which crashed abstract type resolution
• allowed parser\fieldset to contain fields with duplicit name (alias could be different)

Introspection shows arguments for typesystem directives

v0.17.1

codestyle

Input constraint

• New InputConstraint with atLeastOne and exactlyOne settings
• Typesystem directives are now returned via introspection
• Added printing of deprecation reason

Normalizer exceptions are outputable

v0.16.2

codestyle

Code cleanup, tests & exception improvements

v0.16.1

exception cleanup

Constraints for Input fields and arguments.

v0.16

codestyle

Fixed merging of object arguments if default is null.

v0.15.1

fixed merging of default object values if default value is null