[test/ldap] a bit of pep8

[js] add configuration file for jshint (closes #5593987) copied from https://gist.github.com/haschek/2595796

spelling: *aly → *ally

[web] Add a <label> around choices on CheckBox and Radio form widgets Allows clicking directly on the text rather than only on the widget. Closes #7672774.

[web] xml_escape CheckBox and Radio labels (closes #7672764)

[test/tox] Enforce installation of modified yapps 580a6821713d is not enough for tox apparently... The thing is that it will first install dependencies (the `deps` option from tox.ini), actually pulling yapps from Logilab github but then, it will install the project (that is, CubicWeb) from the sdist *along with its dependencies*, which will pull yapps again and override the previously installed version for some mysterious reason. So add a `pip install` command in tox.ini, so that the modified yapps is the last one installed.

[web] delete unused PropertySheet._sourcefile_mtime

[etwist] remove no-longer-necessary uicache cleaning It was done before we were actually up, which means it could be too eager when combined with #6893185. Closes #6893247.

[web] remove PropertySheet._cache Instead of remembering that a css file has been processed, we re-process it at every request. This prevents our cache getting out of date with the file system. Closes #6893185 While we're at it, write the file atomically so that we don't risk serving partial data.

[test] Add missing u'' Test actually works in py3k, but not in python 2... That has to be a first!