Update to Gradle 5.0

[dbuos]

Change project's gradle version to 5.0, this requires to make some minor
adjustments.

Fixes: gh-6148

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[rwinch]

Thanks for the PR @dbuos! This is now merged into master!

[raphaelDL]

I'm trying to build the project locally and sometimes I get the java out of memory exception, I'm not sure if this has something to do. I see that there's a memory limit set

I took a look at: https://docs.gradle.org/5.0/userguide/upgrading_version_4.html#rel5.0:default_memory_settings

when running: ./gradlew clean build integrationTest

I've got messages like:

Execution failed for task 
Java heap space

and

Expiring Daemon because JVM Tenured space is exhausted
Daemon will be stopped at the end of the build after running out of JVM memory

I don't know, what do you guys think? did it happen to you?

[rwinch]

@raphaelDL Thanks for reaching out. I wonder if there is a memory leak somewhere. If you use the --no-daemon does it ever run out of memory?