Add ability to stop the build on a TPC threshold for the Maven plugin

[vmassol]

Add a Maven Mojo (could be called CheckMojo) that can stop the build if the Test Percentage Coverage (TPC) is below a given value, specified as a configuration in the project's pom.xml.

For example Clover does this:

    <plugins>
      <!-- Fail the build if the test coverage is below a given value. -->
      <plugin>
        <groupId>com.atlassian.maven.plugins</groupId>
        <artifactId>maven-clover2-plugin</artifactId>
        <configuration>
          <!-- Note that the overall TPC when including functional tests for this module is around 78% -->
          <targetPercentage>${xwiki.clover.targetPercentage}%</targetPercentage>
        </configuration>
        <executions>
          <execution>
            <id>clover-check</id>
            <phase>verify</phase>
            <goals>
              <goal>instrument-test</goal>
              <goal>check</goal>
            </goals>
          </execution>
        </executions>
      </plugin>

That would help a lot...

[Godin]

Duplicate of jacoco/jacoco#6
Moreover EclEmma project is dedicated to Eclipse plugin.

[vmassol]

Indeed I've used the wrong project (that's why I was surprised to not find an existing issue about this topic!), sorry about that and thanks for referencing the existing issue...