Gradle upgrade to 3.3

[c0c0n3]

We should upgrade to the latest Gradle version: 3.3. (We're currently using 2.12.) It can be done by changing

gradleVersion = '2.12'

in build.gradle to 3.3 and then regenerate the wrapper.

But there's a nasty issue. Our current version of the Gradle Spring Boot Plugin is 1.3.4 and this version doesn't work with Gradle 3.3. In fact, if you try to build with Gradle 3.3 you get this error message:

Failed to apply plugin [class 'io.spring.gradle.dependencymanagement.DependencyManagementPlugin']

This is a compatibility issue that can be easily worked out by upgrading to the latest release
of the Spring Boot Plugin: 1.4.3. (More info about it in the Gradle Forum.) But 1.4.3 brings in a new set of Spring Boot dependencies and with them the following headaches:

• Upgrade libraries #5. Libs upgrade.
• Defaulting plain text MIME type to UTF-8  #3. Defaulting plain text MIME type to UTF-8.
• Gradle Spring Boot Plugin Id #4. Gradle Spring Boot Plugin Id.

[c0c0n3]

rather upgrade to gradle 3.4. set:

gradleVersion = '3.4'

in build.gradle and regenerate the wrapper.

[c0c0n3]

implemented changes in v1.1.0-beta, see #11.