Trigger start and stop of Mesh Tether from within Serval Mesh
Sync serval-dna
Merge branch 'development' into 'andrew'
Improve ./aa script: app-install-alpha et al

Replace 'ai' (app-install) command with 'air' (app-install-release),
'aib' (app-install-beta) and 'aia' (app-install-alpha) commands.
Upgrade Serval DNA
Improve build.xml: terminate if version_string.sh fails

Also fix a bug in version_string in Serval DNA that failed on a non
dirty working copy.