Fix documentation issues so package can install

Just a few quick commits here to fix some issues that were preventing me from installing the package.  Package should install successfully with install_github now: 

```r
devtools::install_github("ropensci/rdataone", subdir='dataone')
```

Mostly very small adjustments to the roxygen documentation.  I also had to fix a cyclic dependency error (a method and a function both called `validate`).  I've also moved the depends list to imports, as CRAN is getting very strict about namespacing now and does not accept depends lists unless absolutely necessary.  

In adjusting the roxygen I've added a few `@include` directives to build the proper collate list to avoid some of the warnings.  One of them looks like it can't trivially be avoided (regarding the class `DataPackage` vs the method `getData`, seems to that each of DataPackage.R and D1Object.R use classes or generics defined in the other file...)