SI-4684 Repl supports whole-file paste

Add a file argument to the :paste command which loads the
file's contents as though entered in :paste mode.

The :paste command is replayable.

Samples, including companions defined together:

```
scala> :paste junk.scala
File contains no code: junk.scala

scala> :paste no-file.scala
That file does not exist

scala> :paste obj-repl.scala
Pasting file obj-repl.scala...
<console>:2: error: expected start of definition
         private foo = 7
                 ^

scala> :paste hw-repl.scala
Pasting file hw-repl.scala...
The pasted code is incomplete!

<pastie>:5: error: illegal start of simple expression
}
^

scala> :replay
Replaying: :paste junk.scala
File contains no code: junk.scala

Replaying: :paste obj-repl.scala
Pasting file obj-repl.scala...
defined trait Foo
defined object Foo

Replaying: Foo(new Foo{})
res0: Int = 7
```

1 files changed, 20 insertions, 0 deletions

diff --git a/test/files/run/repl-paste-4.scala b/test/files/run/repl-paste-4.scala
new file mode 100644
index 0000000000..0060dc1ff6
--- /dev/null
+++ b/test/files/run/repl-paste-4.scala
@@ -0,0 +1,20 @@
+
+import scala.tools.partest.SessionTest
+
+object Test extends SessionTest {
+  def session =
+s"""|Type in expressions to have them evaluated.
+    |Type :help for more information.
+    |
+    |scala> :paste $pastie
+    |Pasting file $pastie...
+    |defined class Foo
+    |defined object Foo
+    |
+    |scala> Foo(new Foo)
+    |res0: Int = 7
+    |
+    |scala> """
+  def pastie = testPath changeExtension "pastie"
+}
+