Add LicenseKey verification

[wojciechczerniak]

Description

We can use the key generator used by Handsontable with a different seed. The rest of the logic will be roughly the same (we, don't have moment.js in HF).

• Add licenseKey field to global config Global settings #58
• Setup a new product in my.handsontable so we can generate keys by hand at least
• License Key will not be generated at the beginning, should be one of the strings mentioned in Add LicenseKey verification #222 (comment)
• "Display" a message. This will be tricky, HF does not have the frontend and throwing an error is far from discreet. It can be caught and ignored. Console.log will be ignored as well. I'm proposing a new #LIC! error as a result for all formulas.

[wojciechczerniak]

String: 'non-commercial-and-evaluation'
String: 'agpl-v3'
String: {licenseKey}
License key messages:

    Invalid license key:

    Console log: The license key for HyperFormula is invalid.

    Missing license key:

    Console log: The license key for HyperFormula is missing.

[wojciechczerniak]

Small change, we're going to need the generated license keys after all.

[wojciechczerniak]

Done in #293 and #299