Modernise ship-with-civi theme

I've opened this issue to see if we can agree on a way to improve the theme that ships with core (or to ship an additional theme with core) without the discussion spinning out into the technical sprawl that always seems to paralyse us on this issue...

Problem statement CiviCRM ships with a theme looks dated and is off-putting to new adopters- some specific criticisms

• Colours are …. Beige. Current fashion would seem to be more white space (also drab in bootstrap)
• Button styling seems dated
• Some people seem to prefer side tabs - not sure if this is consensus

Goal of issue/discussion

• Find some achievable improvements
• Don’t get bogged down on solving everything

Potential solutions

• Improve the Greenwich theme - possibly as a paralell theme - addressing the most egregious issues (e.g just swapping colours / using more white makes it look more modern)
• Add an existing theme to core (Shoreditch, Aah, Finsbury park, Christian’s theme). Note that if we do this
  1. it will mean that the theme becomes part of core codebase & would be maintained as such, with a priority place on maintainability and ensuring not too much css is downloaded (which might not always be in line with the designer’s vision).
  2. bringing an existing theme into core would require the mainintainer agreeing to their theme being forked into a core extension & the core extension being maintained according to core maintenance priorities & principles. This may not be something current theme maintainers want as some design elements are likely to be sacrificed in the pursuit of maintainability / compatibility.
  3. Anything that ships in core must work on all CMS and have acceptable page load speed for anonymouse users.
• Build up a minimal theme - ie what is the min theming we need to do to make it ‘load’ & move the rest of the css to greenwich (this is assuming a minimal theme would be better….)

Note that this ticket #33 covers previously discussion. Those discussions focussed on making it easier for themers to theme CiviCRM whereas the focus on this is what can we do to make the CiviCRM that ships with core look better.