Unify eachcol and columns functions

docs/src/lib/types.md

@@ -45,9 +45,9 @@ The difference between the return value of `eachcol` and `columns` is the follow
 * The `columns` function returns a value of the `DataFrameColumns{<:AbstractDataFrame, false}` type, which is an
   iterator returning the column vector only.
 
-The `DataFrameRows` and `DataFrameColumns` types are subtypes of `AbstractVector` and support its interface
+The `DFRowVector` and `DFColumnVector` types are subtypes of `AbstractVector` and support its interface
 with the exception that they are read only. Note that they are not exported and should not be constructed directly,
-but using `eachrow`, `eachcol` and `columns` functions.
+but using the `eachrow`, `eachcol` and `columns` functions.
 
 ## Types specification