[SPARK-9015] [BUILD] Clean project import in scala ide

Cleanup maven for a clean import in scala-ide / eclipse.

* remove groovy plugin which is really not needed at all
* add-source from build-helper-maven-plugin is not needed as recent version of scala-maven-plugin do it automatically
* add lifecycle-mapping plugin to hide a few useless warnings from ide

Author: Jan Prach <jendap@gmail.com>

Closes #7375 from jendap/clean-project-import-in-scala-ide and squashes the following commits:

c4b4c0f [Jan Prach] fix whitespaces
5a83e07 [Jan Prach] Revert "remove java compiler warnings from java tests"
312007e [Jan Prach] scala-maven-plugin itself add scala sources by default
f47d856 [Jan Prach] remove spark-1.4-staging repository
c8a54db [Jan Prach] remove java compiler warnings from java tests
999a068 [Jan Prach] remove some maven warnings in scala ide
80fbdc5 [Jan Prach] remove groovy and gmavenplus plugin