[webui] convert our css into scss to have one format to rule them all
[api] some optimizations for /webui/all_projects

Before
6284ms (Views: 3298.7ms | ActiveRecord: 720.0ms | Backend: 0.0ms | XML: 0.0ms)

After
426ms (Views: 0.8ms | ActiveRecord: 50.4ms | Backend: 0.0ms | XML: 0.0ms)