Move validate command into doc fragment and fix a few typos

lib/ansible/modules/files/lineinfile.py

@@ -31,6 +31,7 @@ author:
     - "Daniel Hokka Zakrissoni (@dhozac)"
     - "Ahti Kitsik (@ahtik)"
 extends_documentation_fragment: files
+extends_documentation_fragment: validate
 short_description: Ensure a particular line is in a file, or replace an
                    existing line using a back-referenced regular expression.
 description:
@@ -116,16 +117,6 @@ options:
      description:
        - Create a backup file including the timestamp information so you can
          get the original file back if you somehow clobbered it incorrectly.
-  validate:
-     required: false
-     description:
-       - validation to run before copying into place. 
-         Use %s in the command to indicate the current file to validate.
-         The command is passed securely so shell features like
-         expansion and pipes won't work.
-     required: false
-     default: None
-     version_added: "1.4"
   others:
      description:
        - All arguments accepted by the M(file) module also work here.