Preparing for 2.6.1.
[SECURITY-144] Updated the plugin to declare direction of Callables

(cherry picked from commit 1028db2cccb282d3cd53298b246aa6bb0b7fda68)

Conflicts:
	src/main/java/hudson/maven/SplittableBuildListener.java
Changing artifactId.

(cherry picked from commit f6a51b70e2660106275735380bf4bc05b2de909d)
Merge tag 'maven-plugin-2.7' into SECURITY-144-trunk

[maven-release-plugin]  copy for tag maven-plugin-2.7

Conflicts:
	pom.xml
	src/main/java/hudson/maven/MavenBuild.java
Merge branch 'SECURITY-144-trunk'

Conflicts:
	pom.xml