Updated translations

Includes previously hardcoded strings from the template files

Signed-off-by: Tobias Grasse <dotdotfx@gmail.com>
Default header image

Adds a default header image to get rid of the error in browser dev tools.

Signed-off-by: Tobias Grasse <dotdotfx@gmail.com>
Refactored PHPtemplate files

1) Main page regions now use classes instead of IDs to provide reusability and less specificity.
2) Adds Docblocks and consistent space-based indentation.
3) Main navigation now uses a nav tag directly instead of a hardcoded nav wrapping a div.
4) Made all strings translatable.

Signed-off-by: Tobias Grasse <dotdotfx@gmail.com>
CSS refactoring

Major CSS refactoring:
1) CSS debug moved to mm-devtools plugin.
2) Guidance comment blocks are removed because this is no longer the main working file for students.
3) GitHub Updater URI changed to use the muk-mlu-mulitmedia repository.
4) Adds further sensible defaults for the existing regions.

Signed-off-by: Tobias Grasse <dotdotfx@gmail.com>
Updated README

References to the child theme and devtools plugin repositories.

Signed-off-by: Tobias Grasse <dotdotfx@gmail.com>