Angular 9 upgrade

[jeroenheijmans]

Fixes #717

Steps taken:

1. Update to latest Angular 8 stuff
2. Update to Angular 9 with the upgrade cli commands
3. Tweak small things that didn't go perfect during upgrade
4. Update all devDependencies (for one to fix security vulnerabilities)
5. Tweak the readme and change log slightly
6. Bump the version to 9.0.0-RC1 - I presume we'd want to include other PRs too if we're releasing a new version?

Not done:

• Rebuilding (and committing) the docs. This is awkward on a Windows machine, as it touches all files and affects the newlines. Didn't seem needed anyways as the docs only need to be regenerated upon actual release?

[jornare]

This will exclude older angular versions. should probably be as it was unless the new update introduces breaking changes for older versions

[jeroenheijmans]

True! I did do it intentionally but without too much confidence I guess: since there were so many migrations and compiler changes in NG9 (more so than 7 and 8), and since there's limited capacity/enthusiasm in this lib's community to support mixing newer versions of the lib with older versions of Angular.... I guessed that this change may be a good one.

But I suppose we can bring it down again, and consider using v9 of the lib with <v9 angular versions a "no warranty" thing?

Leaving this choice up to Manfred I think.

[yukund]

Hi

Much appreciate for the effort to support angular 9.

Are you going to include this fix in next release?

Our team is going to upgrade to angular 9 soon. I am just wondering if you have a timeframe for next release?

Thanks

[manfredsteyer]

Thanks!