[web/views/formrenderer] do not use `cubicweb:target` attribute on form (closes #5534074) The `cubicweb:target` is a flag indicating that the form data (with file input) shall be posted inside an iframe - this is a well known "ajax-like" workaround to post files with browsers that do not support `FormData` (a.k.a IE<10). The `cubicweb:target` was introduced when CW used the "xhtml strict" doctype. Now that CW uses the "html5" doctype, this namespaced attribute is no longer necessary and the iframe can be generated directly. Before this patch, CW inserts the `cubicweb:target` attribute in the form DOM element (server side) and `setFormsTarget()` updates the DOM with a new `<iframe>` element (client side). Now, CW inserts the `<iframe>` DOM element directly (server side), making `setFormsTarget` useless.

[js] lint : make it explicit that typeof is an operator, not a function. Also, use === / !== except for null / undefined comparison

[devtools] qunit: show helpful data when an assertion fails Related to #5533333.

[web/test] Use shorter $() instead of jQuery() Consistency FTW. Related to #5533333.

[devtools] qunit: use new async testing APIs http://qunitjs.com/cookbook/#asynchronous-callbacks QUnit keeps track of all the assert.async() objects created inside the test functions and expects all done() functions to be called. Failure to do so will result in the test being failed. Unlike .start and .stop which were internal APIs, assert.async() is stricter and fails tests if assert methods are used *after* all done() functions are called (see "test callback execution order"). Related to #5533333.

[devtools] qunit: use new assert APIs test functions now accept an "assert" argument which exposes QUnit's assert methods: assert.{expect,equal,deepEqual,ok} Related to #5533333.

[devtools] qunit: stop using global variables test -> QUnit.test module -> QUnit.module Related to #5533333.