Extend file_sse_pool for multiple chains, don't read SEQRES. Fix output and log.

Stop file_sse_pool reading SEQRES lines; their numbering does not have to be
identical to the numbering in HELIX and SHEET lines, see 3IM3.pdb for an example;
add reading for multiple chains. Extend qs. Fix tests.

Fix output formatting and addition of newlines in log.