Add RebuildDispatcher extension point to allow other plugins to propagate action

[zittix]

This PR is an updated version of PR #44 rebased to latest + fixed for latest changes.

It adds RebuildDispatcher extension point to allow other plugins to propagate action to the rebuild.

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Unit test output:

[INFO] -------------------------------------------------------
[INFO]  T E S T S
[INFO] -------------------------------------------------------
[INFO] Running InjectedTest
[INFO] Tests run: 22, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 11.902 s - in InjectedTest
[INFO] Running com.sonyericsson.rebuild.RebuildValidatorTest
[INFO] Tests run: 13, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 54.337 s - in com.sonyericsson.rebuild.RebuildValidatorTest
[INFO]