Move default setup to CroogoTheme and reorder key hierarchy in theme.json

Theme settings are now stored under a specific `settings` node.
Enable configuring FormHelper's inputDefaults from theme.json
Configurable css classes in theme.json

- Configurations are read during application startup and sent to view as
  $themeSettings
- New helper method: LayoutHelper::cssClass() to retrieve configured values
Adapt helpers to use css class configured in theme.json
Remove hardcoded span10 classes from views
Remove inputDefaults() calls that are not necessary
Avoid hardcoding inputDefault class values
Remove hardcoded span6 for inputClass + relayout
CSS: Replace hardcoded container class
CSS: Replace hardcoded row class
CSS: Replace hardcoded span8 class
CSS: Replace hardcoded span4 class
CSS: Replace hardcoded span12 class