- if mandatory is true, findEtcFile() will abort with a message (via cerr).
This allows a non-existent file to be caught at the lowest level and avoid
error handling in IFstream, which might not be initialized at that stage.
* delay fileName expansion in timeVarying BCs, add the possibility to use
relative directories
* export FOAM_ROOT from argList: "." and ".." for serial/parallel. This
allows us to specify a single movable location regardless of serial/parallel.
* only replace an isolated leading "./" with CWD, strip others. This
improves use for a relative names.