Let the user decide whether they want to view or download an artifact

There are some kinds of artifacts that users would like to open immediately (e.g. log files) and others that they would like to download (e.g. jar files).

Bamboo 1.2.2 lets the browser decide on the appropriate action based on the Content-Type. Bamboo determines the Content-Type based on the file extension, and defaults to text/html if the file extension is unrecognised.

As a consequence of BAM-402, Bamboo 1.2.3 will force the browser to download the file. This is a change in behaviour, and may not be what the user requires.

We should let the user decide by removing the hyperlink from artifact names, and instead offering "view" and "download" links next to each artifact name. We should use the Content-Disposition header to control this.