Setting the project user not possible on installations in subdirectories

[kralan]

In project.js, in line 219, the request url: '/ocs/v2.php/cloud/users/details?offset=0&search=', for getting a list of nextcloud users does not take the path of the nextcloud installation into account. Other urls are constructed with OC.generateUrl() to accomplish this.
As a consequence, editing the project user does work with nextcloud installations in webroot like https://nextcloud.my.domain/ but does not work in installations in subdirectories like https://www.my.domain/nextcloud/ because the list of users cannot be obtained.
This got noticed in #121, but while #121 is a usability annoyance, this problem breaks functionality and can be treated separately.