Joiner.can_join: make sure size of fragments >= 2
source code of Joiner: fix long lines
Joiner: do not keep set of deleted fragments

They are deleted along with block.
Joiner: replace static methods with non-static
FragmentCollection: property "cycles_allowed"
Joiner: use FragmentCollection, test against prev/next
Joiner: disable tests of new version against prev/next
Sequence.set_name(): make sure name doesn't include ' ' or '_'
MergeUnique: fix error if sequence has only 2 fragments

[a, b]

a->next()->next() == a
fix long line
CheckNoOverlaps: use FragmentCollection instead of prev/next
AreBlocksGood: use FragmentCollection instead of prev/next
bsa_algo: use FragmentCollection instead of prev/next
FindBSA: do no use Connector

It is not required now
IsPangenome: do no use Connector
fix long line
MergeUnique: use FragmentCollection instead of prev/next
FragmentCollection: assert argument of add/remove != 0
add processor SliceNless: remove consequent N's from blocks
add more tests for SliceNless

--HG--
rename : test-script/slice-nless/1/in.fasta => test-script/slice-nless/2/in.fasta
rename : test-script/slice-nless/1/out.fasta => test-script/slice-nless/2/out.fasta
rename : test-script/slice-nless/1/in.fasta => test-script/slice-nless/3/in.fasta
rename : test-script/slice-nless/1/out.fasta => test-script/slice-nless/3/out.fasta