Adds Contour ConfigMap Support

[danehans]

Adds support for managing Contour's ConfigMap.

Fixes #38

@jpeach @skriss @stevesloka @Miciah PTAL

[jpeach]

I don't think the template is the right approach here. Contour should expose a package with the Go struct for the config file, and we can consume that directly here.

[jpeach]

xref projectcontour/contour#2621

[stevesloka]

The alternative would be to move the the CRD approach suggested here (projectcontour/contour#2924 (comment)), but is not built out just yet.

[danehans]

@jpeach is it possible to proceed with this approach since this is what's implemented today? I can create an issue that xrefs projectcontour/contour#2621 and projectcontour/contour#2924 (comment) and update the contour-operator when these projectcontour/contour issues are resolved.

[stevesloka]

@danehans I think this is fine to move forward with. The CRD swap is a lot more work and will require a deprecation window that shouldn't hold up this project. =)

[danehans]

@stevesloka I've updated the PR based, PTAL.

/cc @jpeach @Miciah