[FIX] resolved merge conflicts
[FIX] resolved merge conflicts (cont'd)
[FIX] fixed concat iterator for empty stringsets
Merge branch 'master' of github.com:weese/seqan into fix/test_index_stree_iterators
[FIX] reverse-commit peculiar patch
Merge branch 'fix/test_index_stree_iterators' into develop

Conflicts:
	core/include/seqan/sequence/iter_concat_virtual.h