Implementing the files lines count.

New features:
- added the LinesCounter for calculating the files lines quantity;
- count files lines of the selected files in the right table view;
- slot for update the selections rows in the MainWindow class (but this slot
  cannot to set the new values in the model);
- 'Lines' column not display the value, returned the 'stub' function
  FileSystemCustomModel::linesQuantity(). The items in this column is empty;
- in the FileSystemCustomModel class was added an enum 'resHorizHeaderNames'
  for description the existent order of the model columns.

There are need to implement:
- setting calculated count of files lines in the table;
- storing calculated count of files lines in memory and its using, when the
  same file will be selected.

Signed-off-by: Oleg <olgerd27@gmail.com>