[FLINK-2872] [Documentation] Update the documentation for Scala part …

…to add ExecutionEnvironment.readFileOfPrimitives.

Add the missing Scala part for ExecutionEnvironment.readFileOfPrimitives API doc in the
programming guide.

Author: Henry Saputra <[email protected]>

Closes apache#1268 from hsaputra/add_readFileOfPrimitives_scala_guide and squashes the following commits:

f543436 [Henry Saputra] Add variant of ExecutionEnvironment.readFileOfPrimitives in Java with additional delimiter.
1209019 [Henry Saputra] [FLINK-2872] [Documentation] Update the documentation for Scala part to add readFileOfPrimitives.

docs/apis/programming_guide.md

@@ -1721,7 +1721,11 @@ File-based:
   Returns a DataSet of tuples or POJOs. Supports the basic java types and their Value counterparts as field
   types.
 
-- `readFileOfPrimitives(path, Class)` / `PrimitiveInputFormat` - Parses files of new-line (or another char sequence) delimited primitive data types such as `String` or `Integer`. 
+- `readFileOfPrimitives(path, Class)` / `PrimitiveInputFormat` - Parses files of new-line (or another char sequence)
+  delimited primitive data types such as `String` or `Integer`.
+
+- `readFileOfPrimitives(path, delimiter, Class)` / `PrimitiveInputFormat` - Parses files of new-line (or another char sequence)
+   delimited primitive data types such as `String` or `Integer` using the given delimiter.
 
 Collection-based:
 
@@ -1856,6 +1860,9 @@ File-based:
   Returns a DataSet of tuples, case class objects, or POJOs. Supports the basic java types and their Value counterparts as field
   types.
 
+- `readFileOfPrimitives(path, delimiter)` / `PrimitiveInputFormat` - Parses files of new-line (or another char sequence)
+  delimited primitive data types such as `String` or `Integer` using the given delimiter.
+
 Collection-based:
 
 - `fromCollection(Seq)` - Creates a data set from a Seq. All elements