Promoting staging -> Production

[adrianoc]

I've messed with the version numbers so I'll not increase the version number for this release

• updated NUnit 3.13.2 -> 3.13.3, NUnit3TestAdapter 4.2.1 -> 4.3.0-alpha
• updated Microsoft.CodeAnalysis.CSharp (roslyn) to version 4.4.0.1-final
• changed code generation to match roslyn behavior
• updated testing section of README.md
• fixed indirect assignment through pointers (assignment to pointers in fixed statement generates invalid code #184, assiging to pointer parameters does not emit stind instruction #185)
• fixed dtatic automatic properties being handled as instance ones (Static properties are being handled as instance ones #183)
• fixed dorwarded field references generating invalid code (Forward field assignment generates invalid code missing field reference #182)
• fixed edandling of attributes in type parameters (Attributes applied to type parameters are ignore #181)
• fixed forwarded attribute usage (Applying attribute to its own class definition generates invalid code #180)
• fixed branch handling in assembly comparisons
• added support for covariant properties (Support covariant returns #179)
• added support for covariant return methods (Support covariant returns #179)
• added support for modulus operator (%)
• added support for using statement (Support using statements #177)
• use AppendModifier() instead of string concatenation
• resolve actual method instead of the one being overriden
• bumped version to 1.50.0
• made helper method static to be usable in more contexts
• renamed parameter to match its intent
• improved inner type handling
• ensures variable for type definition is registered before processing the type
• moved forwarded method handling to the base visitor