Making entrypoint optional for Java Actions

[kameshsampath]

With apache/openwhisk-runtime-java#14 the Java Actions will be able to infer the entrypoint via Main-Class attribute of the jar. Hence the check https://github.com/kameshsampath/incubator-openwhisk-cli/blob/master/commands/action.go#L512 could be made optional for Java Actions

[kameshsampath]

@csantanapr am not sure we can add this issue to java-runtime improvements epic

[rabbah]

@kameshsampath sorry this sat for so long - looking through apache/openwhisk-runtime-java#20 i think it's orthogonal to the proposed change here. I haven't looked deeper to see if we can implement this already, and you might know faster.

[kameshsampath]

@rabbah am totally lost here.. been very long. If you still see it makes sense to merge please go ahead otherwise knock it off