Make it easier to configure max action exec size for a deployment

To change the max size of the action blob, you have to modify:

https://github.com/apache/incubator-openwhisk/blob/22c0807b9eae20af9acc70b91a1943dd35a95092/ansible/roles/nginx/templates/nginx.conf.j2#L13

https://github.com/apache/incubator-openwhisk/blob/d815394ca5201bab7e7d270af4d471341549c843/core/controller/src/main/resources/application.conf#L57

https://github.com/apache/incubator-openwhisk/blob/658516e6db1bf65ea4bd82e2b5e1ef10f69e0391/common/scala/src/main/resources/application.conf#L345

https://github.com/apache/incubator-openwhisk/blob/e88257ea72dd4341726f50af72e8924fc1ddb966/common/scala/src/main/resources/application.conf#L14

https://github.com/apache/incubator-openwhisk/blob/b3923300638d64b375d8b79dbc268e0ae50a6bf8/common/scala/src/main/scala/whisk/core/entity/Exec.scala#L215

It should be easier to make this change.