Cross-platform fix version.sh

version.sh now works also on linux properly.
Merge pull request #335 from fyrz/version-script-cross-platform

Cross-platform fix version.sh
OpenReadOnly support in RocksJava

Changes:
- new Method: RocksDB openReadOnly(String path)
- new Method: RocksDB openReadOnly(Options options, String path)

Missing:
- Column family support is blocked by #319