Merge pull request #6 from jhunold/master

Fix non-debug builds
Restore Project::id() specific to QtC 3.0

Conditionally compile the id() for QtC 3.0, but setId() for QtC 3.1+
Restore Project::id() specific to QtC 3.0

Conditionally compile the id() for QtC 3.0, but setId() for QtC 3.1+
Updates PR #6
Merge branch 'master' of github.com:mloskot/qt-creator-plugin-boostbuild