[wp-gsoc] [Summer of Code] #355: Separate admin functions into their own class

[Summer of Code]

#355: Separate admin functions into their own class
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 Reporter:  codebykat         |       Type:  task
   Status:  new               |   Priority:  normal
Milestone:  2013 Final (1.0)  |  Component:  Post by Email
 Keywords:                    |
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 As per George: "Consider abstracting out all of the admin functions
 (adding items to admin menus, `add_settings_field()` etc to a second
 function, `Post_By_Email_Admin` and only including it `if( is_admin() )`"

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Ticket URL: <http://gsoc.trac.wordpress.org/ticket/355>
Summer of Code <http://gsoc.trac.wordpress.org>
My example project