enhance cp_menu tab in additional settings vtabs #3959

#3959 

##### Changes

* Added label to the top of the tab pane (was none)
* Renamed option to be more explicit (was "provide", now "create" a menu link)
* Condensed the 3 link options into one-line settings with percentage widths
* Changed label for hover text (was "Description" with help text, now just "Hover text" and no help text)
* Changed label for parent menu link. (was "Which Menu", now "Existing menu")
* Added help box pointing to Build > Menu (was none)
* Shortened Page Layout explanation and exclude this description from new node forms (now only shows on node edit)

### Before

##### Before: (Closed)
![screen shot 2013-10-24 at 2 13 25 pm](https://f.cloud.github.com/assets/228733/1401634/ac00f1a2-3cd9-11e3-9707-664886a44344.png)

##### Before: (Open)
![screen shot 2013-10-24 at 2 13 45 pm](https://f.cloud.github.com/assets/228733/1401647/c50832b4-3cd9-11e3-8d05-54bddec17b35.png)


### After

##### After: (Closed)
![screen shot 2013-10-24 at 2 20 08 pm](https://f.cloud.github.com/assets/228733/1401651/cbd9f67c-3cd9-11e3-8fec-dd99577d596b.png)

##### After: (Open)
![screen shot 2013-10-24 at 2 19 54 pm](https://f.cloud.github.com/assets/228733/1401652/d20409c0-3cd9-11e3-9e70-017def8e6886.png)