Delete confusing Sass main layout partial.

Add fix to prevent horizontal scrollbar when using layout grids to Sass page base partial instead.
Delete obsolete Sass imgrid partial.
Rename Sass container layout to contain…

… to be more generic, to be able to add beside `.ContainPadding` also `.ContainWidth` classes, etc.
Replace all `.Container` classes with `.ContainPadding`.
Add enabled in config check to smartypants (field method) plugin.
Add missing readme to smartypants plugin.
Add calendar plugin.