Pretty much completely rewritten theme with custom HTML translator and a
few parts of the old theme extracted to their own extensions.
Banner images thought not to be that huge after all, and not worth the
hassle of them living in a different repository.
co-authored with @stefanorigano
If the variable was existing outside the context of the ``foreach``,
the value is copied at the end of the foreach into the global context.
Fix#4461 - Q74531 - Q71486 - Q71675
* __content__ can't be used in Python implementation because safe_eval, so use
``0`` from Python implementation instead
* remove postfix from t-call tests because due to implementation details all
whitespace crap following a t-name is added to rendered template in Python
impl, and don't want to normalize whitespace.
* document qweb based (mostly) on JS version
* convert JS qweb tests to (mostly) language-independent XML so they can be
used for JS and Python implementations
* add some more tests (e.g. precedence between t-value and body in t-set)
* remove ``t-import``
* fix parity in foreach(dict) (and rename some variables to make array and
object versions more similar)
Christophe Matthieu