Make expression preprocessing run before some attributes parse them

[danielfernandez]

Currently, the expression pre-processing mechanism is running once an expression is being executed. So there's no way that users can build the values of attributes such as th:each or th:include, th:replace, etc. (see #77 for better reference)

It could be useful if preprocessing executed actually before these attributes split their values into their corresponding parts.

[danielfernandez]

Moved to the Wish List