Improve variables

Added a 'double' variable type for math trig functions (issue #78) and slight sanity checking.
     NOTE:Unresolved problems if different variable types are mixed. Not sure how best to fix this.

So... Better descriptions and changed colors to help visual debugging of different types.

![arduvariables_01](https://f.cloud.github.com/assets/5730290/2005108/ef464a20-86d0-11e3-997e-b8df11e968a0.png)
![arduvariables_00](https://f.cloud.github.com/assets/5730290/2005109/f41b683c-86d0-11e3-8066-a18fe263d8cc.png)