Set BASE_URL of container host

[jonblack]

The base URL used by the soap service in MRS is set during compilation using the makefile variable MRS_BASE_URL; it's value is copied into the generated configuration file.

The default was to set it to the hostname via $(shell hostname) but since MRS now runs in a container, this evaluates to the container's hostname, not that of the host running the container.

For now it's hardcoded. It can also be changed in the admin UI. It would be nice to have this generated correctly.

It's also hardcoded in the configure script, which was also using the same method to determine the hostname.

Moreover, the URL that is given in the Makefile is used for the mrs server address and public SOAP endpoint address, and these may not always be the same (in fact with docker, they never will be). For now this is worked around by editing the config file after compilation to change just the SOAP endpoint address.