study_cohorts_info.sql : removed the not needed column from this query

HAI_vs_GE.Rmd : added the capability of passing in a list

begin.view.xml : added LovCombo and ExtendedLovCombo UI controls

HAI_vs_GE.js :
- removed the requirement of having a non-empty cohort to test selected for running the report
- if a user selects new cohort for training, the dependent combo boxes (time point and testing cohort) are now cleared
- made modifications so that now an array of testing cohort matrices identifiers can be passed in to the back-end
- changed the layout to include field sets to group fields in a more meaningful way
- added 'dummy' hard-coded/disabled variable and assays combo boxes

HAI_vs_GE.css : legend (a field set title) has now rounded corners