[BUGFIX] Use extension signature, not extension key, as container scope

The extension key may contain underscores; these will not be present in the TypoScript. Example: extension key "my_ext" becomes "plugin.tx_myext" in TypoScript.
[FEATURE] Add shortcut method to fetch View configuration for extension by name
[FEATURE] Error handling convention with toggle for behaviour

This adds a default errorAction on Flux controllers and attempts to capture errors and improve the normal Exception-based error feedback - in order to better report issues arising from missing configuration, missing paths, missing files, invalid options, bad Flux form structure etc.
[TASK] Implement a limited back trace for custom error views
[TASK] Do not cache per-page setup to files

The TS is already cached this way - processing is fairly light and the configuration is only processed once per page (or retrieved from internal cache).
Merge pull request #67 from NamelessCoder/controllererrorhandling

[FEATURE] Error handling convention for Flux controllers