WebSearch: change CFG_SITE_URL to CFG_BASE_URL
- Now uses the CFG option CFG_BASE_URL instead of CFG_SITE_URL so that the functional property of CFG_SITE_URL as link builder and representation of the site name is separated.
- Also updates all BibFormat elements using CFG_SITE_URL in this way as well as WebStyle default template.
- Adds a new server variable "absoluterecurl" (previously "recurl") that links in "external" formats such as RSS, DC and NLM.
- Changes the <base /> tag in <head> to be added only when CFG_SITE_URL is not the root domain name.