SciDAVis - Improvements SVN-temp

- Implemented the possibility to specify the decimal separators when importing ASCII files.

- Dropped default value for template argument of Interval to enforce readable code.
- Simplified implementation of Interval a bit.
- Added some unit tests (based on CppUnit, http://cppunit.sourceforge.net).

- replaced "Interval<>" by "Interval<int>" to
increase code readablilty

- fixed some compiling errors in filtertest
- improved code readability a little bit

- Turned Interval into a template so that it can be used for (numeric) types
other than int.
- Generalized AbstractDoubleSimpleFilter to AbstractSimpleFilter.
- Generalized TruncatedDoubleDataSource to TruncationFilter.
- Added Double2StringFilter and String2DoubleFilter.
- Improved Filter test program.

- reorganized the interval-based column attributes code
and added the according signals

- Fixed a bug in Table::importASCII()
- Added Table::exportASCII() to the Python interface.
- Added the possibility to remember the last selected filter in the the ImportASCII dialog.

- implemented attaching a DataSourceAttributes object
to a data source
- changed the signals for inserting/removing rows
in all column data classes from dataChanged()
to the new specific signals

- committing my new DataSourceAttributes implementation
including a smal test program

- implemented Interval::split()