[#6740] Show additional notes on the project import pages

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>
[#6740] Changed tool importer header to just source + label

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>
[#6740] Attach tool-specific extra notes to the ToolImporter for more flexibility

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>
[#6740] add importer extra_notes to individual import form