Improvement of marketplace switching

* Cleared screen after marketplace deconnection

(references OpenFLUID/openfluid#221)
Add of error message for connection problems with marketplaces

* Added checks for catalogs or packages missing
* Displayed message dialog when no marketplace file or no catalogs with packages on repository
* Selected first combo box item after an error

(closes OpenFLUID/openfluid#221)
Creation of the packaging script for market

* Added script file
* Modified packages-src repository structure
* Added observer and dataset sources to tests packages
* Added observer installation case to the MarketSrcPackage process method
* Removed "packages" and "repository" directories from the tests
* Adapted market tests

(closes OpenFLUID/openfluid#174)