Moved link below Custom Tracks in menu
New documentation page on how to add a datahub
Moving this into more general documentation, as it doesn't just apply to www.ensembl.org
Added a link to the new instructions on attaching datahubs
Emboldened some text
Added link to new hub documentation
Changed 'datahub' to 'trackhub'
Moved files into upload directory
Updated links
Moving files back - forgot that we only have two levels in the side menu
Fixed link to trackhub page
Changed any remaining instances of 'datahub' to 'trackhub'
Changed 'Datahub' to 'Trackhub'