Decl ignore

Added to macro pass CS_CONSTRAINT which can be use to constraint generic arguments.

Replaced declaration IgnoreFlags by GenerationKind. Added methods IsInternal and IsDeclared to declaration. Replaced IsGenerated = true by GeneratioKind = GeneratioKind.Internal. Deprecated Ignore, replace Ignore set by ExplicityIgnored, replace Ignore get by IsGenerated, IsInternal or IsDeclared.

Deprecated ExplicityIgnored use ExplicitlyIgnore(). Getting ExplicityIgnored and setting ExplicityIgnored to false don't make much sense anymore.