lcov: Remove CVS artifacts

Replace CVS specifics in the build environment and tools source with
Git mechanisms:
 * CONTRIBUTING and README file now refer to github for the primary
   source location
 * When run from a Git repository, the tools dynamically determine the
   Git version using 'git describe'
 * When installed into the file system, the version information is
   fixed with the current Git version
 * When preparing distribution files, the version at the time of
   preparing the files is written to file ".version"

Also add a .gitignore file to filter out the most frequent temporary
file types.

Signed-off-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>