keep a bit more data when cleaning an ARB DB for PT-server use
* the SAIs HELIX and HELIX_NR in addition to ECOLI
* all of presets/
We need the latter to keep the ARB file sufficiently complete to be opened
by arb_ntree. Previously, GBT_get_alignment_width would fail. NT_repair_DB
would cause a segmentation fault. Keeping all presets costs a bit of
memory/space, but the ability to open a database from lib/pts for
inspection seems more important than saving a few bytes (and fixing
NT_repair_DB much more difficult).
For the same reason, I think HELIX and HELIX_NR should be kept, as they
are expected by BI_helix. Since the cost is negligible, I'd argue for
keeping them just in case.
(Alternative solution, not pursued: always keep a cleaned and a full copy
of the ARB database in lib/pts, possibly changing the suffix on the
cleaned databases to express that they are no longer compatible)