SciDAVis - Improvements SVN-temp

- 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()

Implemented saving/restoring of the last status of extendable file dialogs.

- fixed/improved formula saving

- improved DataSourceAttributes::setFormula()

- implemented column attributes
(masking rows, selections, valid/invalid rows, formulas)