Control temp directory.

[Laurie Nevay]

We currently look for /tmp, /temp, then cwd + temp directories in order to create a temporary director for preprocessing GDML files. It has been requested to control this for use on computer farms where use of /tmp may be problematic even though it exists.

[Laurie Nevay]

This has been added in develop. Now the option can be used:

option, temporaryDirectory="./";

for example. This will replace the previously described vector of paths to be tried.