toaster: naming and description changes

toaster: naming and description changes

Some minor changes to the names and descriptions
used in the Toaster configuration file:

* Change the name of the local layer source from Local OE-Core
to Local OpenEmbedded

* Change the imported layer source name from User Imported Layers
to just Imported layers. It is shorter, which helps table display

* Change the description of the master release from OE-Core
master to OpenEmbedded master

* Change the description of the dizzy release from OE-Core dizzy
to OpenEmbedded Dizzy

* Change the helptext of the dizzy release to remove the
"latest" reference, which can make maintenance hard

* Change the name of the Local Yocto Project release to Local
OpenEmbedded

Signed-off-by: Belen Barros Pena <belen.barros.pena@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>