SVN mergeinfo should be used to determine the original author

Current implementation of the SvnExeScmProvider shows the user who merged branch as changes author.
This pull request uses svn '--use-merge-history' option to extract the original author for each line.

In addition the -Dmaven.scm.svn.options option is added. It gives the ability to specify additional options for svn blame, like '--ignore-all-space' or similar.