Update player page templates, headers for better overall UX and integration with the Spotlight exhibit

[broadwell]

The contributions to the develop branch so far have gotten the app much closer to the ideal experience, but there's always more that could be done. Such as:

• Use a big header layout for both the Play and Perform modes. I.e., it should be a version of the FullHeader header layout with 3 header bands: Stanford header band, Stanford University Piano Roll Archive band, and the header links band.
• Then create a third mode, called "Embed", that is basically just the Play mode, but with only the current single-line minimized header (this mode would be used when, you guessed it, embedding the player on other pages)
• Make the control strip icons bigger (up to 2x as large as currently)
• Use unbounded icons for the control strip, e.g., just a triangle for Play, rather than a triangle with a circle around it, then maybe use CSS to draw borders around each button.
• Font and color scheme cleanup: make sure the different color profiles and CSS variables are being used wherever possible; stick to the same 2-3 fonts for the entire UX.
• Generally try to unify the appearance of the big header in the Play/Perform/Search/About templates with the Spotlight exhibit's header as much as possible. This also involves some changes to be made to the Spotlight site configuration, and regardless the two site's headers can't be made 100% equivalent, but some ideas are:
  • The header's HOME button always links to the Spotlight site (https://exhibits.stanford.edu/supra)
  • Roll Archive Features might go away, or be replaced with a different link to explanatory content
  • Both sites should have a header link to the Pianolatron's Search page
  • FYI the search bar in the current Spotlight site probably will go away
  • The Pianolatron's Search page might become the default landing page for the app, rather than /homepage

[broadwell]

This is all pretty much done!