biovel flavour
ajax callback to get and display data file preview - OPSK-20

ajax fetches json details about datafile and displays it in a preliminary preview. Ajax is triggered when the select box is changed.
Preview is cleared when no data file is selected. The preview can easily be changed as it is handled javascript function and displayed according to a shared partial.
moved the DataFileInput concern into its own library file - OPSK-20
slightly improved formatting of the run input text

the text that says where the data originated from if it came from a data file, fixing the link problem and removing the bold.
some minor refactoring

removed some complexity of data_file_controller#data
libpq-dev gem neeed for postgresql
Merge branch 'biovel-workflow-work4'
openseek flavour