Support for mutli-domain setup's.

At the moment the CIVICRM_UF_BASEURL is used to create most of the links and redirects. It's value is only determined once during installation and then set as a constant in the configuration file.

When using multiple domain's to access one civicrm installation, only one of them can be fully supported. The others are redirected to the 'main' domain which implicitly logs the user out (as the session cookie is not set for this domain).

I implemented a patch that (optionally and by default) tries to guess the right protocol/host/port combination and falls back to CIVICRM_UF_BASEURL if this is not possible.

$config->userFrameworkBaseURL (which essentially is CIVICRM_UF_BASEURL) is used pretty often in the whole application. Most of the times this usages could be replaced by using either relative paths (some/page) or absolute paths (/some/page) instead of full URLs (http://server:port/some/page) .