[webui] port to possibly_empty_ul

This avoids duplicating conditions
[api] rename bs_user_id to user_id in all tables
[api] put the user login in the fixtures instead of the id

Same for roles
[dist] update spec file template to buildrequire procps
[webui] add test case that repository links
[webui] ignore empty arrays for main page statistics
[webui] fetch source files directly from backend
[webui] mls wants other icons for incidents
[webui] add a test case for /monitor events