Remove all instances of DATA_PATH from the sources and use pResource_Manager instead.

[Quintus]

The compiled-in fixed resource path is now history. Instead, the resource manager determines the current executable’s path and retrieves the data directory from there (unless you use the FIXED_DATA_PATH compilation option to force a specific directory). However, there are still far too many references to DATA_PATH (whose definition I’ve already removed) in the sourcecode which must go.

[Quintus]

With the merge of the purge-data-dir branch, DATA_DIR is now history and boost::filesystem::path is used everywhere.