feat(moment-date-adapter): implement strict mode

[MatthiasKunnen]

Moment supports a strict flag which solves a lot of parsing errors. This PR allows setting this flag.

Why
Despite specifying a format, moment is very forgiving in the date strings it perceives as valid. Examples:

Input	Format	Forgiving	Strict
1/2/2017	M/D/YYYY	2017-01-02	2017-01-02
1/2/2017	MM/DD/YYYY	2017-01-02	Invalid date
2/1/2017	MM-DD-YYYY	2017-02-01	Invalid date
Januar 1, 2017	MMMM D, YYYY	2017-01-01	Invalid date
Jan 1, 2017	MMMM D, YYYY	2017-01-01	Invalid date
2017-1-1	MMMM D, YYYY	2017-01-20	Invalid date
2017/12/24	MMMM D, YYYY	2017-01-20	Invalid date
2017/12/10	MMM D, YYYY	2017-01-20	Invalid date

Note
The moment docs state

In a later release, the parser will default to using strict mode.

This implementation follows the flag's default value in Moment(strict off). When Moment changes their default, the moment-date-adapter will follow.

[crisbeto]

It looks like the this._options is used in a few places. Consider moving into a variable since it should minify a little better.

[MatthiasKunnen]

I've attempted to do so. Let me know if it needs further change since I'm not sure this is what you requested.

[MatthiasKunnen]

@crisbeto, is the refactor as you requested?

[MatthiasKunnen]

Anything holding up this PR @mmalerba?

[mmalerba]

We run all of the PRs against Google's codebase internally to make sure that they don't break any apps or tests. This one is waiting to be run

[brgrz]

When will this be released as a new version, literally we need it right now :)

[mmalerba]

This will be included in the next minor release. These generally happen ~1/month

[brgrz]

@mmalerba I've just updated to 8.1.3 that was release 6 days ago and I don't see the strict option in it. Am I missing something?

Update: I can see here it wasn't included https://github.com/angular/components/releases/tag/8.1.3 Why would that be?

Update: Actually under commits I can see it was included but when I download 8.1.3 from npm the updated code is not there..only useUtc option exists.

[MatthiasKunnen]

@brgrz, that is due to semantic versioning. 8.1.3 is a patch release. As this pr adds a new feature, it will arrive in the next minor release. See also the label, target: minor. Strict mode will arrive in 8.2.0.

You can read more about Angular's versioning here: https://angular.io/guide/releases

[MatthiasKunnen]

@brgrz, 8.2.0 has been released. You can now use strict mode.

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