Description of problem:
Need a REST API to request the log directory of a cartridge.  Currently, we have to make an assumption on the location of the log directory.  Ideally, we would be able to look this up on a cartridge property.

Although there maybe be a property that contains the log directory of a cartridge, there is no way to know the property is the log directory.  For instance, the node-js cartridge has properties":[{"name":"OPENSHIFT_NODEJS_LOG_DIR","description":"Directory to store application log files.","type":"environment"}]  But we can't count on the existence of _LOG_ in the name to properly identify the environment variable.