Merge branch 'release-0.1.17' into development
Added section numbering to the user manual.
Add an option to number cells from left to right (in progress).

The code to grade the exams numbered from left to right is still
pending.
Left to right numbering in the detection code.
Add a survey mode (issue #16).

It needs some testing before closing the issue.
First experiments with pyqt.
Add a toolbar to the test Qt gui, and testing status labels.
Create a menu and improvements in the toolbar.
Tests with the status bars.
Improvements to the interface.
Add the ability to register listeners in the Qt interface.
Many improvements in qtgui, including a "new session" dialog.
Improvements to the new session dialog.
Many improvements to the session management mechanism.

- First version of the eyegrade module connected to the new GUI.
- Sessions can now be stored and loaded.
- Other improvements in the new GUI.
Add the transitions from search mode to review mode.
Change answers in review mode, capture keys and fix an error.
Save and discard capture. Improvements to close session.
Add the manual detection mode.
Notification when closing without saving.

Closes #35.
Dialog for editing the student id.