Various improvements to the build process including support for self-contained builds. * Note that despite all of these changes PARPG still does not run because asset paths are not standardized, * Modified the SCons script so that by default running `scons` with no arguments creates a self-contained "build" under a build subdirectory to make in-source testing easier. To install PARPG, use `scons install` instead. * Got rid of the binary launcher and replaced it with a shell script for unix and a batch script for Windows (batch script is untested). The binary turned out to be too much trouble to maintain. * Modified the parpg.settings module and parpg.main entry script so that PARPG searches through several default search paths for configuration file(s). PARPG thus no longer crashes if it can't find a configuration file in any particular search path, but will crash it if can't find any configuration files. * Paths supplied to parpg.main are now appended as search paths for the configuration file(s). * Changed the default configuration file name to "parpg.cfg" to simplify searches. * Created the site_scons directory tree where SCons extensions and tools should be placed. * Created a new SCons builder, CopyRecurse, which can copy only certain files and folders from a directory tree using filters (files and folders that start with a leading dot "." e.g. ".svn" are ignored by default). * Added the CPython SCons tool (stands for Compile-Python - I didn't name it!), which provides the InstallPython builder for pre-compiling python sources before they are installed. However, it is currently broken and only installs the python sources.