Use svn log with xml output to resolve encoding issues (as reported in issue #62)

As reported in issue #62 there are troubles with svn log and character encoding. It is AFAIK impossible to force an encoding in the svn command line tool for svn log. However, svn log with the --xml option will generate utf-8 encoded output (and is more save and easier to parse IMHO).
resolved copy paste bug

replaced erroneus $$ by $
Minor cleanup, exception handling for xml parsing, coding guidelines compliance

- compliance with coding guidelines
- added exception handling for xml parsing
- removed unnecessary echo </pre> after return logic in import_full
- removed unnecessary loop and checking for numerical return value of process_svn_log_xml (this seems to be not required for a while since the process_svn_log in the current form does not return a numerical value either)
Merge pull request #68 from philippschaefer/patch-1

Parse SVN log as XML