Update the installation section; fix some broken urls
Update the installation section; fix some broken urls

pavlovicnemanja92/superdesk,ioanpocol/superdesk,petrjasek/superdesk,superdesk/superdesk,superdesk/superdesk,gbbr/superdesk,darconny/superdesk,petrjasek/superdesk,petrjasek/superdesk,mdhaman/superdesk,superdesk/superdesk,darconny/superdesk,gbbr/superdesk,ioanpocol/superdesk,hlmnrmr/superdesk,mdhaman/superdesk,mugurrus/superdesk,pavlovicnemanja/superdesk,pavlovicnemanja/superdesk,pavlovicnemanja92/superdesk,mugurrus/superdesk,pavlovicnemanja/superdesk,superdesk/superdesk,hlmnrmr/superdesk,mdhaman/superdesk,hlmnrmr/superdesk,pavlovicnemanja92/superdesk,petrjasek/superdesk,pavlovicnemanja/superdesk,pavlovicnemanja92/superdesk,ioanpocol/superdesk,darconny/superdesk,gbbr/superdesk,pavlovicnemanja92/superdesk,mugurrus/superdesk