Fix outstanding issues in map browse page

[luistoptal]

User story

Fix issues in page http://gigadb.gigasciencejournal.com:9170/site/mapbrowse

• Tabbing shows some broken unstyled controls
• there is an img with missing alt
• there is no h1
• the dots in the map are not focusable
• Consider increasing map height

[only1chunts]

NB ticket #831 needs to be done before the map browser is of much use