Change default JavaScript infrastructure provider from Prototype to jQuery

The Prototype JavaScript Framework has been the default JavaScript infrastructure provider (see SymbolConstants.JAVASCRIPT_INFRASTRUCTURE_PROVIDER) since Tapestry 5.4.

This issue is about changing the default to jQuery, mainly for the following reasons:

1. to reflect today's reality that jQuery is by far more popular than Prototype, and hence Tapestry users are more likely to use jQuery rather than Prototype;
2. to align the default js provider with the default css framework (Bootstrap), which requires jQuery.

NB not to forget to update the Javadoc of SymbolConstants.JAVASCRIPT_INFRASTRUCTURE_PROVIDER