Predicate to filter out ignored objects

[itamar-marom]

Fixes #4

Description

Instead of filtering CRs in the Reconcile function, we want predicates to filter them out.

This PR deprecates the Spec.Ignored and handles the ignore functionality with the annotation druid.apache.org/ignored. When the value of this annotation is "true" the object will be ignored. Any other value will reconcile the object.

The API still exists to avoid breaking change.

Also, the logic of the Spec.Ignored in the Reconcile function has been removed, and a new function has been added to the predicates.

Also, some consts has moved to new file - types.go

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This PR has:

• been tested on a real K8S cluster to ensure creation of a brand new Druid cluster works.
• been tested for backward compatibility on a real K*S cluster by applying the changes introduced here on an existing Druid cluster. If there are any backward incompatible changes then they have been noted in the PR description.
• added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• added documentation for new or modified features or behaviors.

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Key changed/added files in this PR

• predicates.go
• handler.go
• types.go

[AdheipSingh]

Thanks LGTM.