LRDOCS-1197 Establish ExternalContext (JSF) content from Dev Guide
LRDOCS-1192 QAed and updated screenshot.
Merge branch 'LRDOCS-1192' of https://github.com/mwilliams2014/liferay-docs into jsf-edits
LRDOCS-1192 Edits based on QA
LRDOCS-1197 Edit ExternalContext (JSF) tutorial