[TASK] Throw RuntimeException if no template is selected

This patch makes the PageProvider throw an RuntimeException when the (FE context only) method getControllerActionFromRecord() resolves an empty template reference.
[BUGFIX] Analyse full root line of pages to know main/sub template

This patch fixes an issue where if a page is a subpage of another page and that parent page defines "template for subpages" but the current page sets its own "template for this page", the field to define values to use for sub pages would not be displayed.

Problem is solved by continuing to analyse the root line of pages even after a main controller action has been found.
[TASK] Clean up unnecessary code
Revert "[BUGFIX] Analyse full root line of pages to know main/sub template"

This reverts commit ba76a479dcb9ccb6c1c34c1a8ea6c1c6bdff0a94.

The reverted commit breaks rendering of subpages that dont define their own action because the returned action used will be that of a parents page main action.
[BUGFIX] Provide ext conf in ext_tables
Merge pull request #176 from hmspl/extconf

[BUGFIX] Provide ext conf in ext_tables