Improve explanation of portal object

[jsi]

This page: http://xp.readthedocs.io/en/stable/reference/view-functions/index.html is not very understandable. It lacks context and an overview, and there should be a link to the JavaDoc (http://repo.enonic.com/public/com/enonic/xp/docs/6.11.0/docs-6.11.0-libdoc.zip!/module-portal.html), with an explanation of the difference between the 8 functions listed in doc and the 22 in the javadoc. Also: please answer these questions that have come up in the courses we have held for customers, on that page:

• Is "portal" a reserved name?
• How and Where to use ${portal.something} in Thymeleaf
• Architecture (where does portal object come from?)

[jsi]

@Bellfalasch requested this documentation. It came up during a training session. (Feedback from TDM meeting.)

[Bellfalasch]

@ComLock Does this look right? Since you got the questions you know best.

I guess 1) and 3) are the important ones, 2) is more or less covered as far as I know.