Ability to use Date objects and numbers as values for model, min and max properties of Datetime

[gamtiq]

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• It's submitted to the dev branch and not the master branch
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix: #xxx[,#xxx], where "xxx" is the issue number)
• It's been tested with all Quasar themes
• It's been tested on a Cordova (iOS, Android) app
• It's been tested on a Electron app

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

Other information:

It is inconvenient that model for Datetime component should only be string in special form.
So I have added ability to use Date objects and numbers as values for model, min and max properties.

[rstoenescu]

Hi,

Thanks for taking time for a PR!

Can you separate the datetime work from the previous one? Always make a new branch before doing a PR. This PR contains both datetime and the build stuff. Thanks!

[gamtiq]

Close in favor of #477