[MNG-6207] display deprecation build warning for dependencies with scope 'system' declaration

[dejan2609]

JIRA ticket: MNG-6207: Create WARNINGs in case of using system scope

Note: this PR is created instead of #119

@khmarbaise: FYI

[khmarbaise]

First build has failed based on violated checkstyle rules. So best is before you open a pull request to run a full build via mvn clean verfiy on the whole Maven project...the checkstyle rules will be checked as part of the build...

[khmarbaise]

Second build after fixing the checkstyle issues has worked. Integration into master done. You can close the pull request. Thank for your help to make Maven better.

[dejan2609]

Just for the record: somehow it slipped of my mind that package phase doesn't execute integration tests (http://maven.apache.org/ref/3.5.0/maven-core/lifecycles.html#default_Lifecycle) and hence this checkstyle error pass unnoticed on my side:

[ERROR] src/main/java/org/apache/maven/model/validation/DefaultModelValidator.java[471:104] (blocks) LeftCurly: '{' should be on a new line.

Thanx @khmarbaise for this correction and for overall review.

[dejan2609]

Just one more thing that I recalled from my memory: I did tried to execute tests (http://maven.apache.org/core-its/core-it-suite) like this: mvn clean test -Prun-its but I received warning that profile doesn't exist:

[WARNING] The requested profile "run-its" could not be activated because it does not exist.