Upgrade to latest Serval DNA

Internal refactoring to fix potential SQL injection vulnerabilities
Suppress logging when MeshTether is not installed
Stop trying to turn on Hotspot when it turns off immediately
Latest Serval DNA changes
Improve build.xml: check version strings

For Alpha, Beta and Release builds, the version string produced
by the version_string.sh script must have the proper form
Sync serval-dna for alpha build