Adaptive control point positioning to prevent a cusp.

(transplanted from orage/2ec166afa6771d78ff3b62f8ee339ad5516c7a89)
Added 'statusMessage' property to the widget/node.

(transplanted from orange/49a8be8076a9ed724cfcead2d1f3cebe33b407d8)
Fixed width column file creation from tab separated file.
Added three demo widgets and a widget template to documentation
Moved fixed_from_tab from datasets to data.
Added FixedWidthReader and tests as preparation for LazyTable.
Added read_cell() to FixedWidthReader.
Fixed some comments.
Removed debug print messages.
First version of LazyTable and OWLazyFile classes.
Ensures test works from any directory for automated testing.
Use cls instead of Table whenever possible so the code works with derived classes.
Create LazyTable from domain.
Fixed count_lines, do not count the header lines.
First attempt to support X, Y, metas. What is the __len__ of half a table?
Populate the data with some values on initialization.
Added todo.
Added refcheck=False to _resize_all(). Shouldn't break anything
that isn't broken already.
Store rows properly. Default to materialized len.
Better preloading. Put name back.