[tools] g_sans - add trajectory avereging

This change adds
1. trajectory averaging for s(q) and p(r)
2. can compute s(q) and p(r) for each frame

Change-Id: Ieb421a8b5ae06b72442bbe5fbae4231a7fa9c980
Signed-off-by: Alexey Shvetsov <alexxy@omrb.pnpi.spb.ru>
Merge "[tools] g_sans - add trajectory avereging" into release-4-6