croaking when '--(db)host' isn't passed, adding -D to the list of options recognized for --dbname (after MySQL), improving readability of the dba_opts data structure

Adding the method is_chromosome to the Slice object. This kind of method is not nice but does deal with a lot of issues with seq_regions being attached to chromosome coordinate systems which are infact unassembled regions.

Header function should not be responsbile for the addition of a > for the FASTA header. That's the serailisers responsiblity. Also removed major DB dependency

Header function should not be responsbile for the addition of a > for the FASTA header. That's the serailisers responsiblity

Only remove tables which are bak and backup to avoid untintentional removal of temp tables like tmp_individual_genotype