Merge pull request #154 from PX4/file_test_fix

Fixed #153 - when no microSD card is present, test used to hang, now abo...
Printing error reason in warning
Merge pull request #148 from PX4/adc_integration

Selected adjustments / fixes to make old apps compatible with new-style ADC
Merge branch 'master' of github.com:PX4/Firmware into sunday