JBrowse feedback: add genericized name to the button to access JBrowse

[carolinebridge]

Feedback from a demo with Lincoln: not everyone would know what "JBrowse" means and not know to click the button when they need a genome viewer.

Proposed change to the button that is used to access JBrowse to maintain the JBrowse logo but change the text to say "genome viewer", and equally so for the "tab".

There's a bit of the JBrowse branding maintained here, but we could also add a "powered by JBrowse" link to expose the name. We could also add the JBrowse logo with the name somewhere, but more UI would need to be drafted for that if that is desired.

Possible mockups:

Link or button might work here, possibly with the logo.

[carolinebridge]

random follow up: could be a more subtle watermark over the bottom right corner too