Fix heights

[pb82]

provides a fix for #93

Adds a compatibility option (spec.compat.fixHeights) for dashboards that have panels with a height property encoded as a number. The Grafana SDK expects a string here. Also, newer Grafana versions don't seem to emit this property in exported dashboards anymore.

This is provided as a switch because it manipulates the json before submitting and we'd usually try to avoid this.

Verification steps:

• take the dashboard from this comment and add it to a CR: Cannot process dashboard  #93 (comment)
• deploy grafana and try to import the CR. It should fail.
• update the Grafana CR and add

...
spec:
  compat:
    fixHeights: true
...

• after a while (max. 30 seconds) the dashboard should get imported successfully

[yogeek]

I confirm that this is working correctly with the compatibility flag