Now defaults to 16 on both frontend and backend.

Co-authored-by: techknowlogick <techknowlogick@gitea.io>

* hide: 'New Project board' button

* there is no reason to show the button for users that are not signed in

* update template: specifies the condition together with another one

as per lafriks' suggestion in the comment

* chore: add proper user authorization check

* chore: also hide button if repo is archived

* chore: show project board edit/delete menu to authorized users only

* chore: drop the redundant IsSigned check

* CanWriteIssues and CanWritePulls implies (and requires) signed in user

* Add CanWriteProjects and properly assert permissions

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: jaqra <48099350+jaqra@users.noreply.github.com>
Co-authored-by: Kerry <flatline-studios@users.noreply.github.com>
Co-authored-by: Jaqra <jaqra@hotmail.com>
Co-authored-by: Kyle Evans <kevans91@users.noreply.github.com>
Co-authored-by: Tsakiridis Ilias <TsakiDev@users.noreply.github.com>
Co-authored-by: Ilias Tsakiridis <ilias.tsakiridis@outlook.com>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>