v1.4.0

This release is larger than usual: lot of small fixes, and a few improvements as
well.

config: change debug mode warning to info
fix: add support for callable expression in event handler (for example, t-on-click="some.function")
fix: allow specific props to override generic props (in t-props)
fix: add support for short object description in inline expressions: { hey }
fix: add support for t-att-value on <textarea/> and <select/>
fix: slots: issue with scoping in nested loops
fix: slots: default slot is not lost in some cases
fix: do not shadow an error in case the finalizing code fails
imp: qweb: allow multiple class in class attribute object notation: t-att-class="{'a b': value}"
imp: better detection for dynamic component change (less need for t-key)
fix: router: allow querystrings in path
fix: qweb: add support for template strings
fix: qweb: make sure nodes with t-transition are removed in all cases

Provide feedback