[JBIDE-15280] Update parent/pom.xml version to 4.2.0.Alpha1

update parent pom.xmlversion 4.2.0.CR1-SNAPSHOT - > 4.2.0.Alpha1-SNAPSHOT
Merge pull request #6 from dgolovin/JBIDE-15280

[JBIDE-15280] Update parent/pom.xml version to 4.2.0.Alpha1