Finish upgrading Gradle wrapper from 2.0 => 2.1

Commit 4d4787d updated the Gradle wrapper config from 2.0 => 2.1, but
did not actually update the wrapper properties file (forgot to run
`gradle wrapper`). This commit finishes what was started there.
Improve UI
Fix withdrawal list update problems and payout amount
Add linux java8 install commands
Update controlsfx to be compatible with latest jdk
Merge branch 'master' into native

In order to pick up the upgrade to the latest version of controlsfx,
which is compatible with the latest JDK8 (8u20).