Add "raw log" link to coin/logview pages

Logview pages like [1] have button to show full log, however for analysis it's more convenient to use raw text file without UI framing, and with possibility to download it and use tools like grep. Page is well aware of log file URL, as it's downloaded with a separate request, so it should be easier to add one more link.

I know that this link is available from respective "coin/integration" page, however sometimes people share links to logview and it's not possible to move from logview to integration page.

[1] https://testresults.qt.io/coin/logview/qt/qtbase/19ee5d50a6417a06311bf9def9518ace0d62cbb5/WindowsWindows_10x86_64WindowsWindows_10x86_64MSVC2017qtci-windows-10-x86_64-16-bae3dd/f8930b3a2d099dccbf3965271755acd446c51007/build_1582802213