Improvements to Test Case Importer usability/UI

Improvements to Test Case Importer usability/UI:

In both file type importers:

• When cancelling the open file dialog it should not clear the previous value.

• There should be a possibility to easily import a new file after an import is done.

• There should be a clearer way to access the documentation.

• Enter key should trigger the "Next" button.

• When selecting a project to import into, if there is only one available it should be selected by default

• Tab button should jump to next field and not to the "Next" button

• When the import has been done the link to the issue search page should list the imported issues by key ascending

In the CSV file importer:

• It should accept special characters such as "\t" as separators.

• It should validate if the encoding is a valid one.

• Not clear the file when going back from the second page to the first page of the importer

• Save last selected encoding and delimiter choices in user settings

• Provide CSV line number in the result of the import