Make @addTagHelper, @removeTagHelper and @tagHelperPrefix optionally accept quotes around their values

[NTaylorMullen]

We made a change to the addTagHelper, removeTagHelper and tagHelperPrefix directives to disallow quotes around their values. This happens to really mess with tooling when using rc1 with rc2+ bits. Not to mention, it doesn't hurt to have quotes. We should allow them optionally like we did in RC1.

/cc @DamianEdwards

[Eilon]

1. Let's re-add support for quotes, but make it some kind of warning.
2. Open a bug for RTM to remove all support for quotes.

[DamianEdwards]

@NTaylorMullen pls ensure you work with tooling to ensure their RC2 release supports both quotes and without (if anything special is required at all).

[mikes-gh]

@NTaylorMullen Yes I noticed VS complains without quotes with squiggly red line after these changes

[pranavkm]

@DamianEdwards we haven't added warnings to the editor as part of this change (an API to send warnings isn't available as yet). We silently read and ignore quotes. Do you think this warrants a follow up work item?

[DamianEdwards]

I think we should just support both and be done with it. No need for warnings.

[pranavkm]

Great, that's how it behaves now.

[Eilon]

Do we need to close out any bug that says to remove/alter the warning behavior in the future?

[pranavkm]

Nope. All we need to do is delete this comment - #636 (comment)

[Eilon]

Ah ok cool (leave the comment there, just say we didn't do it.)