Clean up of data model

- TodosReportStatistics stores copy of input lists and returns unmodifiable lists.
- This cleans the XML structure in stored build.xml.
- The update is backward compatible.
Cleanup of build log messages

- "[TODOs Plugin]" is put at the beginning of each build log message from this pluggin.
- Warning messages contain "WARNING:" prefix.
- Error messages contain "ERROR:" prefix.
- New messages added.
- If no file is matching the searching pattern, processing is stopped immediately and empty statistics are returned(TodosReportStatistics.invoke()).
- If copying of report files to build directory fails the build will be marked as failed.
Code cleanup

- TodosParser.findExceptionMessage() rewritten.
Long paths in results table

- <wbr> element is put after each slah to the paths to allow text wrapping. This solution looks much better than additional spaces and the paths can be simply copy-pasted as with no <wbr>.
- All major browsers except IE support <wbr> at the moment. All informations are displayed in IE, only the first collumn may be extremely wide. This is not our issue, it's Microsoft's one.
Put patterns to <pre>

- Patterns are displayed inside <pre> the same as code - preserve spaces, unproportional font.
Code cleanup

- Results URL moved to one place in TodosConstants.
- Quick changes to have more readable code.
- Javadoc updates.