Fix example SA permissions

The service account used for examples had permissions for all namespaced
Triggers resources but not `clustertriggerbindings`. With the switch to using
listers instead of making direct API calls this means that the EL will keep
printing out error log messages about not being able to fetch
clustertriggerbindings. To fix this, I added updated the SA with the right
ClusterRole and Binding.

In addition, some of the examples were using their own roles/SAs/bindings.
Instead of updating those, I created a single `rbac.yaml` file and added
symlinks to it from the examples.

Fixes tektoncd#846

Signed-off-by: Dibyo Mukherjee <[email protected]>

Updated README for trigger selector based examples

Revert "dibyo's point about only EL sink/interceptors reading secrets"

This reverts commit 8eb2067.

Turns out, the webhook does need access to create secrets since it uses it
to create `tekton-webhook-certs` if it does not exist.

Fixes tektoncd#803

Migrate all usages of template.name to template.ref

Signed-off-by: Dibyo Mukherjee <[email protected]>

Merge annotations on created resources

In tektoncd#712, we added a feature to propagate annotations added to the EL to its
underlying resources. However, this resulted in infinite reconcile loops since
the deployment controller will add a standard revision annotation that the EL
controller will keep trying to overwrite. To fix this, this commit switches the
annotation propagation to merge any annotations set on the underlying resources
before adding any extra annotations from the EL.

Fixes tektoncd#752

Signed-off-by: Dibyo Mukherjee <[email protected]>

Add TriggerCRD object validation and default

Defaults and Validation for TriggerCRD object have been added.

Remove deprecated params from TriggerTemplate

Switch to validating the parsed JSON mmatches.

The marshaled JSON output is flaky, this ensures that it matches after parsing.

Modify spec params to avoid confusion between resourcetemplates and t…

…riggertemplate params

Add Support for Embedding TriggerBindingSpec in EL

TriggerBindingSpec can be added to EventListener Trigger