support of start_with and count to do paging. Fetching the datasets will return totalCount property - hence the need to upgrade to pybis 1.8.4

Upload dialog: layout enhanced, progress indicator added, error reporting implemented inside the dialog

added controlled vocabulary when datasettypes are fetched. added experiment and properties to dataset upload. added some debug information on server side.

complete connection management. Change of connection alters datasetTypes. Altering of datasetType will affect upload form

added writeMetaData() function
removed some unused code and variables

changed XMLHttpRequest to new fetch request which returns a promise. createFeedback() is now taking care about creating feedback boxes.

changed all send_error to self.write({ }) JSON messages. If a sample or datasSet was not found, status is set to 404.