#245: added ProjectStatistic model
#245: rescue RecordNotUnique error
#245: remove average_build_time and build_count columns from Project
#245: updated views and etc
#245: fixed BuildList#average_build_time method
#245: rollback some changes of BuildListObserver
#245: added specs for ProjectStatistic model
Merge pull request #246 from abf/rosa-build:245-individual-build-statistics-for-every-architecture
 #245: Individual build statistics for every architecture
[#247] small refactoring build lists controller
Merge pull request #248 from abf/rosa-build:247-refactoring_build_list_controller
 #247 Small refactoring build lists controller