Removed unneecessary value storages for integer and string values

We store all numerical values as doubles (for simplicity reasons). Strings are non-existant so this issue does not arrise.
Simplified the gui example program a bit by using convenience getters for R/P/Y
Added handling of all variable types in log data element access

Also, added a friendly warning in the comments for FP16. This type has been implemented, but I have no idea if it works the way I think it does. I'm 75% sure this is working, but will check back once I find time for it. Be careful when using it at the moment.