Updating for Mint and Ubuntu

This rebases #258 on top of master, including the necessary commits from #51.

I also fixed an issue with the testCore output. I just took the original version from @bentoogood without the /dev/null bit, and it ran fine on CentOS 6 gcc 4.1.2. The echo change from @propersquid didn't actually run the tests, it just echoed the test program name into the text file.

@johnhaddon, can you confirm this all compiles and tests pass on OSX?

@propersquid, I think you may still have crashes with `scons testCore`. If it does work, you should end up with output in test/IECore/results.txt that look something like the following:

```
Running 355 test cases...
WARNING : ComputationCache::get : Inconsistent hash detected.

*** No errors detected
```