Revised Type class to better document BindingFlags behavior

[rpetrusha]

Revised to document BindingFlags behavior

This PR corrects a number of inaccuracies in the Type documentation:

• BindingFlags.Static and/or BindingFlags.Instance are not sufficient to get a return value. Either BindingFlags.Public and/or BindingFlags.NonPublic must also be used.
• The methods that return an array don't return null.
• Supplying a value of 0 for a BindingFlags enumeration member seems confusing. I've replaced it with BindingFlags.Default.
• Numerous other changes.

Fixes #2052

//cc @tarekgh @GrabYourPitchforks

[rpetrusha]

Closing and reopening to begin new build.

[tarekgh]

@steveharter may help reviewing the changes here.

[mairaw]

I left some comments re. the style rule for flag enums but it doesn't cover all of them.

[rpetrusha]

I wasn't able to batch merge your suggestions, @mairaw, so I did them in a separate local commit. Thanks for the suggestions.

[mairaw]

LGTM