Bug fix: Exon spreadsheet RTF download

Bugs:
1. Full inron sequence not exported in RTF even if selected from config
2. Translated sequence not coloured black in RTF

Fixes:
$hub->param return an empty list if the parameter doesn't exist. Thus the $config hash was losing information in case any parameters is missing. Using // to make sure the hash is formed correctly.
Wrong arguments were provided to get_viewconfig. Fixing the order.
fullseq is also needs to be configured (this is needed to print introns correctly)