allow plugins to use widgets lib

[farfromrefug]

I have plugins that use classes from the nativescript widget libs.
Now i want to publish the plugin with the java sources directly.
If i do that i need to add widget-release to the dependencies.

Now i could do that in the plugin include.gradle, it will make plugin build to work however then app building wont work because the widgets lib will be included twice

So the best solution is automatically add it here.
I am not happy about the path thing, however it will work in all cases.

PR Checklist

• The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/CONTRIBUTING.md#commit-messages.
• There is an issue for the bug/feature this PR is for. To avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it.
• You have signed the CLA.
• All existing tests are passing: https://github.com/NativeScript/nativescript-cli/blob/master/CONTRIBUTING.md#contribute-to-the-code-base
• Tests for the changes are included.

What is the current behavior?

What is the new behavior?

Fixes/Implements/Closes #[Issue Number].

[farfromrefug]

Ok so actually find a way to declare the dependency without needing this.
Anyway that might get useful.
Let me know if you still want that PR

[janoshrubos]

@triniwiz do you see anything wrong with this change? (i.e. increased apk size, etc..)