some more cleanup on pullrequest + release notes update

+review REVIEW-5170
Some doc updates + fixing failing userguide sample

- added default "" to sonar.tests if tests are empty. offers convenience to
customize the sources (see userguide - sample)

+review REVIEW-5170
some more cleanup on sonar-runner.

- remove trace printlns
- add some content to advanced sonar runner sample
- add test java subproject with no sources to smoke integrationtest

+review REVIEW-5170
User receives useful error message when configuring a task in a model block and it is not found

+review REVIEW-5153
don't use java 7 only api in integration test

+review REVIEW-5170
add custom 1.6 compliant inheritIO for better test diagnostics

+review REVIEW-5170
Merge pull request #319 from lptr/master

Expose Project.exec(Action) and Project.javaexec(Action)
Changed GccVersionDeterminer so that it can extract the default target architecture for gcc/clang.
Moved targetPlatform up to BinaryToolSpec and use this to decide whether to pass -fPIC to the GCC compiler or not.`
GCC can build x64 binaries on Windows in general, so remove this check. Still need to improve detection of whether what we find in the path can build x86 or x64 binaries or both or neither, but this is true of Linux and OS X too.
Some notes about native binary improvements.
Some updates to the native binaries chapter:

- Listed a few 'unofficially supported' tool chain + platform combinations.
- Added some details about what you need to install in order to build on various platforms.
Listed a few more things we should add to the CI build
Minor spec update
Some tweaks to error handling and logging.
Moved some open issues and test cases to separate stories.
Garbage collected a completed story.
Reworked the initialisation code in InetAddressFactory.
Fixed broken unit test on windows.
Fixed broken int test on linux.