Make CreateVersionFile git aware

Completely remove svn relateded calls [closes klemmster/libavg_svn_migration#10]

@uzadow  @oxullo 

what was branchurl being used for? I'm assuming it's not needed anymore, as there are no explicit urls to branches in git anymore.

The generated version.h now looks like this:

// version.h
// This file is automatically generated by CreateVersionFile.py

```cpp
#define AVG_VERSION_RELEASE     "1.8.0"
#define AVG_VERSION_FULL        "1.8.0-fix/createVersion.py/bf60517ff4362152b52df1dc89766ee01b7a40f6"
#define AVG_VERSION_BUILDER     "richy@flux Linux-3.14.4-1-ARCH-x86_64-with-glibc2.2.5"
#define AVG_VERSION_BUILDTIME   "2014-06-03T22:48:57.386320"
#define AVG_VERSION_REVISION    bf60517ff4362152b52df1dc89766ee01b7a40f6
#define AVG_VERSION_MAJOR       "1"
#define AVG_VERSION_MINOR       "8"
#define AVG_VERSION_MICRO       "0"
```