Merge pull request #9 from dgwave/master

Test for os and use 'ceylon.bat' if Windows
Implement string for GoalSet
Add license annotation in module.ceylon
Merge branch 'master' of github.com:loicrouchon/ceylon.build
#4: Add GoalGroup support in ceylon.build.task
#4: Test for GoalGroup definition
#4: GoalGroup engine integration
#10: Allow compile Tasks to take multiple compilation units (modules / files) in input
Test for #10
#4: Test for GoalGroup orchestration