refactor versionName

with a leading 'v' in the versionName, which is written to code.xml of our projects (tag: applicationVersion) an upload to either production server (pocketcode.org) or testservers is not successful (webteam uses a php function to compare versions, and this should be something like 0.9.8... instead of v0.9.8...)!

however, the versionName schema differs in local builds and jenkins builds.
local -> 0.9.8-96-g082c2c5 master
jenkins -> 0.9.2001, where 2001 is the jenkins buildnumber

since we use the tag for local builds, which is 0.9.8, I adapted projectVersion, which lead to consistent versionNames on Jenkins like 0.9.8-2001.

if we agree to use a different format in the future (e.g. major.minor.buildnumber), this can be reverted, but we should use a different git tag as well (should be adapted from x.y.z to x.y then)

here is a testrun: https://jenkins.catrob.at/view/All-Categories/view/Catroid-multi-job/job/Catroid-Multi-Job-Custom-Branch/1869/
have a look at the .apk filename (can be found in the build artifacts from Catroid-build-and-test-source # 2399) - catroid-debug-0.9.8-2399.apk; other branches have something like catroid-debug-0.9.2430.apk which is misleading, because our current version is 0.9.8