datatables changes to allow width specification and dTable function

Added width in javascript to specifically change through jQuery the table width.  The code reads chart$params$width first and then chart$params$table$width.  This should allow us to use multiple charts and tables in a single HTML file and limit changes to only the table in question.

@ramnathv also suggested adding a dTable function similar to the other libraries.  This will allow quicker table building.

```
dt <- Datatables$new()
dt$addTable(iris)
```
can now become
```
dt <- dTable(iris)
```