Improved plugin's style sheets guide.
Plugin tutorial part 1 revised.
Plugin Tutorial 1 download link changed from zip to new GitHub repository.
Plugin tutorial zip updated (in case someone linked to it.)
Plugin tutorial part 2 revised.
Plugin tutorial part 1 screenshots redone.
Plugin tutorial part 2 screenshots updated.
Abbr zip files updated, samples now included.
Plugin ACF guide updated, new zip added.
Plugin Stylesheets article revised.
Timestamp tutorial revised, screenshots and zip file updated.
Plugin SDK intro created, Timestamp tutorial moved to 'sample' folder, references added.
Merge branch 'master' into ckeditor-sdk