CSV import does not work correctly for files that contain additional empty lines at the end of the file

[gkronber]

This leads to an exception but can be handled easily.

[mkommend]

r6740:

• Corrected TableFileParser to handle empty rows correctly.
• Refactored DataSet to store values in List<List> instead of a two-dimensional array.
• Enable importing and storing string and datetime values.
• Changed data access methods in dataset and adapted all concerning classes.
• Changed interpreter to store the variable values for all rows during the compilation step.

[gkronber]

r6742 improved handling of empty rows partially reverting changes in r6740.