Work on DateTime code

[josesimoes]

Description

• Remove NewObject function. New DateTime objects are now created using type descriptors.
• Add UTC and ticks mask to properly set/clear tick values.
• Improve checks on all parameters in DateTime constructor.
• Replace individual calls to get DateTime members with a single function that receives a parameter requesting the date part.
• Update mscorlib assembly declaration.

Motivation and Context

• Code improvements.
• Follows Rework DateTime struct CoreLibrary#103.

How Has This Been Tested?

Screenshots

Types of changes

• Improvement (non-breaking change that improves a feature, code or algorithm)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

Signed-off-by: josesimoes jose.simoes@eclo.solutions

[nfbot]

Hi @josesimoes,

I'm nanoFramework bot.
Thank you for your contribution!

A human will be reviewing it shortly. 😉