/media to /static conversion

WIP for /media -> /static conversion. Including:

* `{{ MEDIA_URL }}/path/to/file` -> `{{ static(path/to/file) }}` in templates
* `{{ media(path/to/file) }}` -> `{{ static(path/to/file) }}` in templates
* `mv media/* static_src`
* <del>`url(/media/path/to/file)` -> `url(/static/path/to/file)` in less/css</del>

IIUC, jingo-minify only supports using source files in the root `static` directory [ref][1]?

[1]: https://github.com/jsocol/jingo-minify/blob/d2ffefbd/jingo_minify/management/commands/compress_assets.py#L18