Added SDK for the rest of the learning paths.
Code debugged and complete.
Fixed image border.
Began first part of tutorial.
Added image defining UI security.
Completed first part.
Completed first draft of 2nd step.
Completed first draft of 3rd learning path.
Added next learning path to Next Steps.
Added IDs
Merge branch 'learning-paths'

Conflicts:
	develop/learning-paths/articles/02-writing-a-data-driven-application/04-implementing-a-ui-with-taglibs.markdown
Merge branch 'master' of github.com:liferay/liferay-docs
Merge branch 'number-headers-update' of https://github.com/ngaskill/liferay-docs into pr-210-LRDOCS-1324-number-headers-update
Removed commented code, add <type> to Lists, rebuild JAR file.