Allow download of files

Some assessments use file downloads to provide data (usually alongside programming questions). The inbuilt android webView does not provide a download manager, so we need to add functionality to allow the downloading of files.

Start by locating where the Android WebView is created and configured, then trace how assessments are loaded. Verify the expected behavior for a file-download link, including whether the downloaded file can be accessed by the user; the issue does not name specific files or tests.

Written by the indexing model from the issue text.