[IMP] Remove arbitrary file upload limit (25Mb) and turn it to an option (Fixes #14824)

The hard coded limit dates back to a time where the browsers would crash
when using FileReader#readAsDataURL() on files of serveral dozens of Mb.
This limit is now obsolete and even IE Edge now supports the FileReader
api.

This commit removes the limit and turns it into an option so it's
possible to limit a particular binary field to a given amount from the
form views, eg:

    <field name="image" widget="image" options='{"max_file_size": "200k"}'/>

Note: this feature only works when the FileReader api is available.
      At time of writing, all major browsers supports this feature:
      http://caniuse.com/#search=FileReader

0 files changed, 0 insertions, 0 deletions