Numeric literals (binary and digit separators)

[khyperia]

This PR implements binary literals for C# and VB, as well as digit separators (underscores) for both C# and VB. It also implements a feature check and two /features flags for binary literals and digit separators, again for both C# and VB.

[khyperia]

This implements proposals #215 and #216

[dnfclas]

@khyperia, Thanks for signing the contribution license agreement so quickly! Actual humans will now validate the agreement and then evaluate the PR.

Thanks, DNFBOT;