Make all custom templates work in override mode

[ywarnier]

Current behavior

New templates in main/template/xyz/ must have all the .tpl files from main/template/default/, otherwise fatal errors appear all over the places. This creates issues when updating Chamilo as new files appear in main/template/default/ which are not documented and generate fatal errors for portals updated on the basis of a custom TPL.

Expected behavior

Creating a new template and maintaining it should just be a matter of redefining one or two .tpl files in a separate foder in main/template/. It should not be necessary to have all files present to make it work correctly.

Steps to reproduce

Create a template from a copy of the main/template/default/ folder. Remove one file from that copy. Navigate to a page that uses that file as part of its template -> error.

Chamilo Version

1.11.x 20170921

[ywarnier]

Apparently, this was already fixed by @jmontoyaa in 83df547

[ywarnier]

I'm adding another small change allowing the main/template/overrides/ folder to be checked before going into other templates.

[CesarCavazos97]

Hi, I have a problem with this, when adding an override for the templates on "layout" folder, it doesn't recognize the changes but with other folders works.
Anyone knows how to fix it?