SciDAVis - Improvements SVN-temp

- Improved import of Origin files having date/time data.
- Improved handling of date/time data format in Tables.

- moved the data type specific signals from
AbstractDataSource the specific derived classes

- removed AbstractDateDataSource and AbstractTimeDataSource

- fixed missing "public:" in CopyThroughFilter
- added ": public QObject" and "Q_OBJECT" in AbstractColumnData
again since it won't compile without
- replaced DateColumnData and TimeColumnData by one class
DateTimeColumnData which can store both times and dates
- added ReadOnlyTableModel
- added a small test program for ReadOnlyTableModel
- replaced at() by value() in all ColumnData classes

Added labels to input ports of filters.

- Improved documentation of filter classes.
- Added convenience overload for AbstractFilter::input().
- Added DoubleTransposeFilter and a demonstration of how to combine it with StatisticsFilter for row statistics.
- Added QwtDataFilter, a small glue class for Qwt.

- Fixed several technical problems in the Docbook sources.
- Added auto-generation of Qt Assistent profile (for OpenJade).

- Implemented feature request #3443 (better default paths on Linux).
- Fixed MultiLayer layout problem with Qt 4.3.0.

- Fixed Bug #11220: Segv when changing table/column names.
- Fixed bugs in deleting project folders.
- Fixed crashes in Table::sort() due to a bug in Table::loadHeader()

Solved some constness problems and improved test program.