Issue #1078 Gradle Task to create executable fatJar

[kishansagathiya]

This commit adds a gradle task which will create an executable jar
with all the dependencies

Fixes #1078

[kishansagathiya]

@mkalinin
I was able to create an executable jar without using a dependency like Shadow.
Eventhough, I have raised this PR, I have a feeling that you either don't want a task to create executable jar( because you removed shadowJar). In which case, feel free to close this.
Any reason for removing shadowJar? Does this PR help?

[coveralls]

Coverage decreased (-0.1%) to 55.91% when pulling b01c4ac on kishansagathiya:issue_1078 into bb0d8b6 on ethereum:develop.

[zilm13]

Yeah, we've removed shadowJar plugin because it was conflicting with our main build. Your approach looks functioning but I'm not sure it will keep working after changing some dependencies. Anyway it works now and let's keep it!

[zilm13]

I'd keep all in filename, it's more common

[zilm13]

@kishansagathiya No need to do everything in one commit next time. It's better to see changes in separate commit according to review and not a big deal if we have 2+ commits for one pr.