Add test to dump hits from MultiSegment-MultiCollections example. Investigate issue: https://github.com/AIDASoft/DD4hep/issues/141 for details

Fixes for warnings from doxygen
proper list layout
verbatim around xml examples
escape unknown tag
remove copy/pasted doc for non-existent parameter

No code changes. Common code formatting removing tabs, replacing with spaces (tab-size=-2) + emacs reformatting.