Add Event and Data (observed variables) file in ISA export

[bdartigues]

Now the last version of ISA-Tab for phenotyping exxperiments includes an Event file and a Data file that list all events and all observed variables numerical measures in exported experiment. Events and obsserved variables are already listed in Investigation file in STUDY PROTOCOL section.

[bdartigues]

Event data are handled by ISA-tab export. Observed variables measurement will be linked with experimental design. Observation structure has been enriched with three new fields: measurement, unit and trait.