Allow for users to manage their personal setting in a separate settings page

[Sebastiaan127001]

Usability-wise profile management and user settings are in a menu in the top right.

I suggest that there is a page where users can manage the following settings:

• Language ENG / NL - see also https://github.com/ICTU/quality-time/issues/3158
• Time and Date format US / EUR (see the standard for this https://en.wikipedia.org/wiki/ISO_8601 )

[eric-nieuwland]

Please consider to support at least the following date formats:

• YYYYMMDD (i.e. ISO 8601, should be the default IMHO)
• DDMMYYYY (rest of the world)
• MMDDYYYY (US) Possibly with added seperators, e.g. '/' or '-'.

Time with seconds and optional seconds fragment (if available).