auto-generate expense sheet by using title and number

- before create a new instance checks if the current testsuite has an old one
- re-uses file-dictionary functions of frontend software checks
- minor fixes

/reviewed-on !615

Display relation field select list if focus is activated
Fixup click handling

(fix: e46ade7a)

(fix erp5.git/eb5f1fb1)

As it is a common pattern to set validators on hidden fields
to display custom errors to users.

By using `os.path.normpath` we also support paths with a trailing slash.

Also, change the JSON format and update tests according to these changes

The script though that user was scrolling the test output while in reality we just
add a tiny difference of 0.5 pixel.

/reviewed-on nexedi/erp5!632

Fixes dropbox app key in officejs media player.

/reviewed-on nexedi/erp5!628