no need to override method transcript_display_xref_sources - diplay xrefs are done in OfficialNaming.pm for zebrafish

Two commits. First is to use a custom factory to let us default to embl, genbank dumps and allow user override [ENSCORESW-226]. Secondly our pipeline was not RC_NAME friendly. We now inherit the default options from hive generic conf and add our own [ENSCORESW-225]

[ENSCORESW-224]. Fix for multi-line SQ lines caused by large sequences being pushed through SeqDumper. Was never an issue before as our slices were never big enough. Applied the same fix to Genbank but it should be less of an issue due to it's formatting meaning we need larger slices to cause the issue.

Added a single warning for running without a CCDS database, and provided an exit for certain no-data situations.

Tests null cases and basic functioning of sorting algorithm.

New utility object for finding canonical transcripts. Refactoring of "set_canonical_transcript.pl" logic.

added method remove_source_priorities; it's called from xref_mapper.pl when option -recalc_display_xrefs is used

changed option -recalc_display_xrefs to boolean, it wasn't possible to recalculate display xrefs without using the xref db

slight memory requirement adjustements as well

set_display_xrefs deleted, no need to override this method as gene and transcript display xrefs are set separately in DisplayXrefs.pm

can be run across several hosts at a time

[ENSCORESW-220]. Being removed in favor of our new generate_default_aliases.pl code for the production DB.