Added Oracle Linux 6.3 x86_64 Base Box

Hi Gareth,

I have added an Oracle Linux 6.3 x86_64 Base Box. Please review and merge;-)

NOTE: I put a link to the base box [Build Notes with detailed information](https://github.com/terrywang/vagrant/blob/master/oracle64.md) (on github) which could be very useful to people (who want to know how it is built, would like to install Oracle Database). If it is inappropriate, remove it;-) 

Terry