Categorize the parameters in 'passenger start' so that the help message is more readable
Add forgotten #include
Small changes to categorizations in the documentation

[ci:skip]
Add configuration directives for enabling sticky sessions

Partially solves GH-1194.
Invalidate old sticky session cookies
Document sticky sessions

Closes GH-1194.

[ci:skip]
Have the Meteor loader check whether sticky sessions are enabled
Document that the 'meteor' app type is only for non-bundled Meteor apps
The Node.js loader should signal successful startup after calling the app's listen callback, so that any exceptions there are properly reported