Replace Bower with CDN jsdeliver.com

see:

• https://discuss.tryton.org/t/state-of-the-dependencies-of-the-web-client/3441/8
• #13359 (closed)

note that given this creates a network dependency, i wondered if one might not instead prefer to have js dependencies handled thru like package.json. i wasn't so sure on ideas so far on that specifically, so i figured i'd maybe get this out there to start that conversation.