[FEATURE] More informative error page with troubleshooting info
[TASK] Use new shortcut method to get stored variable from page template
[TASK] Make PageConfigurationProvider return extension key of carrier extension

This analyses the page record being rendered and returns the extension key related to the page template currently selected or inherited.
[TASK] Don't isolate detection of PageConfiguraionProvider to fluidpages scope
[TASK] Simplify custom controller handling in Page Controller
Merge pull request #33 from NamelessCoder/serviceunification

[TASK] Use renamed Services from Flux
Merge pull request #32 from NamelessCoder/controllererrorhandling

[FEATURE] More informative error page with troubleshooting info
[TASK] Switch to renamed Services from Flux
[TASK] Simplify PageConfigurationProvider by using new Flux Service
[TASK] Adjust PageConfigurationProvider resolve call to new Flux logic
[TASK] Implement getExtensionKey in PageConfigurationProvider

This allows the ConfigurationProvider to read the extensionKey as specified either in TypoScript or automatically due to having registered the collection's extension key in PHP.
[TASK] Use Flux Service to get native View setup
[TASK] Add native extension key to setup if not already defined
[BUGFIX] Check for presence of error page template before rendering it