Added new expiration profile "Conversation", changed office activity type + new activity "call centre"

Changes: New expiration profile, called conversation. Derived from weighted averages of Breathing (2/3) and Talking (1/3). Modified the office/meeting activity profile (UI) to use conversation instead of talking. Introduced a new activity profile Call Centre (i.e. everyone talking all the time) to replace old office/meeting - main use case for this is for benchmarking existing calculations, but might also be useful for CoTrac.

Closes issues #96 (closed) and #93 (closed).

I tried not to break anything but @gaazzopa if you could take a look before the merge that would be super.