Make core themes consistent in the way they are set up

[Kristina Hoeppner]

The core themes differ to some degree in how they have been created because they had to be created while we were still actively developing on the Bootstrap changes. Therefore, certain elements are implemented differently across themes, which makes it hard to keep them all updated and having the same styles etc.

Pat suggests to make things more consistent for these themes so it's also possible to inherit from every theme (currently, Ocean can't be inherited from).

This would also help make things easier for themers.

e.g. consolidate some variables (group navigation bar also works out of the box in subthemestarter).

[Mahara Bot (dev-mahara)]

Patch for "master" branch: https://reviews.mahara.org/7273

[Mahara Bot (dev-mahara)]

Reviewed: https://reviews.mahara.org/7273
Committed: https://git.mahara.org/mahara/mahara/commit/66d234c520a0f105c181e6656d0204d537dc578a
Submitter: Robert Lyon (<email address hidden>)
Branch: master

commit 66d234c520a0f105c181e6656d0204d537dc578a
Author: Pat Kira <email address hidden>
Date: Fri Nov 25 16:40:20 2016 +1300

Bug 1637371 - Consilidating raw theme colours

- Amend Ocean theme implementation similar to other theme so new theme
can inherit from it

- Ensure that all colour values in scss components are variables (except
those that are more specific)

- Remove select2.scss as it is now part of raw theme for theme-ability
- Also remove select2.css inclusion in PHP files
- Add scss version of select2 styles and remove existing one
(_select2.scss)
- Create _mahara-select.scss for style override

behatnotneeded: styling only

Change-Id: I624b55ce34dd19ad525ba250877780bfbc0251b5