Simplifying use of ApplicationContext framework

[Joilnen]

Proposal
try to avoid internal root exposing to user application as much as possible, no break the actual interface,
changed the Bootstrap.cpp tutorial if it is accept I change the rest

[paroj]

try to avoid internal root exposing to user application as much as possible

why do you think this is beneficial? The Root object provides access to some important functions like the WorkQueue. Also it is a Singleton, so it is not really hidden..

[paroj]

also you accidentally reverted some recent changes in master

[Joilnen]

also you accidentally reverted some recent changes in master

My intention is avoid to expose root as much as possible, and to leave only ScaneManager as point of interaction with Ogre less failing points, the other features from Root I think to wrap them in ApplicationContext, and made applications created with this framework smaller and easier.