Changed the read-line command

Previously, the read-line was performed using the stream-operator. Unfortunately, this approach limited the possible reading range to a word, causing problems when parsing files with blanks between the quotes and separators.
Instead, the readline is performed using the readLine() method of the QTextStream class.
Fixed a problem with the csv-import.

During the import, the parser used to append blanks between quotes and separators as part of the cell-content.
Now blanks are detected and ignored, iff they are not used as separator or in between quotes.