BF and ADD: Many iohub related changes

* Many eye tracker related updates:
   - eyetracker independent validation process, handles graphics presentation and eye position accuracy calculation and results display.
   - handling of missing data in eye tracker sample events is now consistent across eye tracker versions.  Same value is used to indicate missing data i gaze fields, and same status field value is set if the sample is missing data / invalid.

* Changed iohub demo folder structure.

* Auto connect of ioSync on Linux now works.

* Fixed TextBox import issue left over from removal of unused file.