documentation: poky-ref-manual, dev-manual - deveshell handling

Fixes [YOCTO #2909]

Updated the "Using a Development Shell" in the dev-manual to note
that the OE_TERMINAL variable is the thing that controls what
terminal is spawned.  Added a reference into the new
variable description.

In the poky-ref-manual, I created a new glossary description for
the OE_TERMINAL variable.

(From yocto-docs rev: 25001eba312c4109b4aaa79b334d27e144ef0d3f)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/dev-manual/dev-manual-model.xml

@@ -1862,35 +1862,8 @@ directory.</para></listitem>
         This command spawns a terminal with a shell prompt within the OpenEmbedded build environment. 
         The <ulink url='&YOCTO_DOCS_REF_URL;#var-OE_TERMINAL'><filename>OE_TERMINAL</filename></ulink>
         controls what type of shell is opened.
-        You can define the variable in the <filename>conf/local.conf</filename> 
-        configuration file in the <link linkend='build-directory'>Build Directory</link>.
     </para>
  
-    <para>
-        Current available terminals are:
-        <literallayout class='monospaced'>
-     auto
-     gnome
-     xfce
-     rxvt
-     screen
-     konsole (KDE 3.x only)
-     none
-        </literallayout>
-        The default terminal type is "auto" and causes 
-        the OpenEmbedded build system to attempt to spawn terminals in a 
-        priority order until one is found that is available on the host 
-        development system.
-        For the case of an X terminal, <filename>DISPLAY</filename> must also 
-        be defined.
-    </para>
-
-    <para>
-        If <filename>OE_TERMINAL</filename> is set to "none", the system 
-        never spawns a terminal under any circumstances. 
-        Use this setting when you are doing automated builds.
-    </para>
-
     <para>
         For spawned terminals, the following occurs:
         <itemizedlist>