Introduce a beta channel tag and logic for driver binary versions

[jason-edstrom]

Introduce a beta configuration tag to separate the event of getting latest stable vs latest beta.

[jsmithe]

Noticing some failures after the latest updated to driver 81 because it is in beta channel

webdriverextensions/webdriverextensions-maven-plugin-repository@99d63ea

We could test against this locally but our CI build server isn't going to use beta versions of Chrome. So for now we will have to specify the 80.x version.

[jason-edstrom]

I misread the main site. I can revert the changes for the other repo or we can keep it as it is.

[jason-edstrom]

@jsmithe I reverted the change. You should be in the clear. Sorry for the hang up.

[sephiroth-j]

In most cases we are speaking of Chromedriver and the beta version of today is likely to become the stable version of tomorrow.

I would keep it simple:

• separate the beta drivers into a their own repository file
• add an option to include beta drivers
• if this option is enabled, the beta-repository file will be loaded as well and merged into the list of the stable drivers
• if the beta-repository includes a newer version of a driver than the regular (stable) then the newer (beta) version will be used, otherwise the (newer) stable version