Wrote comments for CommonHelper.
supress ugly exception message and print out a more user friendly message.
Set log level to error message, when exception with conflicting top level corpus
raises.
reformat the output of the annis-admin
Use the nice images help messages from the cli packages for init.
Print usage, when required parameter are missing for the init commad.
introduce a new flag "-o" for the import command
fixes #42

There is introduced a flag '-o' for overwriting the conflicting top level
corpus. Also the logging output for annis-admin.sh is reformatted and more user
friendly and clean then before.
Before adding the pdf-viewer style to a grid event, check if a pdf viewer is
available.
Filter the event styles in EventExtractor is the more general solution and make
it easier to apply the page number event to kwic.
fixes #145
AutoGeneratedQueries -> ExampleQueriesPanel
Check, if a corpus is selected. If not take the one from the query.

fixes #139