allow for nested layouts, (multiple nested embed tags)

[ovresko]

allow for nested layouts, (multiple embed tags)
cases where nested layouts (embed) are required: post.django -> layout.django -> index.django
renders post.django with layout = {"layout","index"}

~post.django

My awesome post that renders inside layout, that renders inside index {{embed}}

~layout.django

My awesome layout {{embed}}

~index.django

{{embed}}

[gaby]

@ovresko Can you add a test for this?

[ReneWerner87]

@ovresko friendly ping

we need additional tests and also the correction of the current tests

[ReneWerner87]

@ovresko friendly ping

[ReneWerner87]

@ovresko friendly ping