deposit: assets cleanup

Changes js import clauses to use url_for
I have just changed to use url_for. There is a problem with hogan for deposit. It is also loaded in page_base.html in global_javascript, but the one from page_base seems to be loaded to later, and js/deposit/templates.js cannot find it.

The solution seems to be moving all js from webdeposit_assets block to global_javascript block.

I actually have some problems with paths of js files when I use deposit templates as the base for the overlay's ones, and this commit seems to fix them. That's all. It also does improve the code. I would rather have it merged, and if you want to discuss about duplicated hogan.js, we can prepare a next commit to fix this problem.