Templatize image pull secrets and provide value from values.yaml instead of permanently hardcoding them

[msafwankarim]

Implementation for #176

Following is the flow

Copy value from source imagePullSecrets;
Set Pod Image Pull Secrets to template
Set the source value in values.yaml

Benifits

This would add the imagePullSecrets in pod spec by default. If there were any values in the imagePullSecrets field it will add them to values.yaml