Memory: Added memory used by processes.

Signed-off-by: matematik7 <domen.ipavec@z-v.si>
Docs: Documented /api/memory/processes

Signed-off-by: matematik7 <domen.ipavec@z-v.si>
Dashboard: Implemented memory page.

Signed-off-by: matematik7 <domen.ipavec@z-v.si>
Dashboard: Added memory usage history.

Signed-off-by: matematik7 <domen.ipavec@z-v.si>