theme/e/shelf: Add a translucent style.

This adds a translucent style for e shelf.
@feature
test_genlist: Add elm_genlist_item_subitems_get sample.
multibuttonentry: use !strcmp() instead for comparison.

Reviewers: seoz

Subscribers: seoz

Differential Revision: https://phab.enlightenment.org/D1680
actionslider, app, bg: Fix and clean up doxygen documentation.
box, bubble, calendar: Fix and clean up doxygen documentation.
clock, datetime, dayselector: Fix and clean up doxygen documentation.
colorselector, entry, flip: Fix and clean up doxygen documentation.
gesture_layer, glview, hover: Fix and clean up doxygen documentation.
icon, image, label: Fix and clean up doxygen documentation.
layout, list, map: Fix and clean up doxygen documentation.
panel, prefs, progressbar: Fix and clean up doxygen documentation.
scroller, slider, slideshow: Fix and clean up doxygen documentation.
thumb, toolbar, web: Fix and clean up doxygen documentation.
win: Fix and clean up doxygen documentation.
elm: Clean-up and fix a lot of doxygen for elementary headers.

- Keep consistency.
- Use addtogroup that works well and convenient.
- Make struct/enum/union look correctly on the doxygen.
DBUS Menu: fixing SIGSEV and SIGBUS when trying to use dbus.

Summary:
Using of dbus menu causes a weird exception that looks
like this (for example in function elm_win_main_menu_get(Evas_Object *win)):
> EINA: Data at address 0x0 is invalid. Replacing with zero page.
> mmap: Operation not permitted
> ERR<22270>:eina_mmap lib/eina/eina_mmap.c:110 _eina_mmap_safe_sigbus()
> Failed to mmap() /dev/zero in place of page. SIGBUS!!!
> Aborted (core dumped)

This issue appears because there is a lot of places where Elm_Object_Item is
used, but it should be Elm_Menu_Item_Data.

This issue could be reproduced with elementary_test:
1. run elementary test with dbus enabled.
2. find "Systray Item" button and click on it.
3. get SIGSEV in your console.

@fix

Reviewers: cedric, raster, seoz, Hermet

Reviewed By: Hermet

Subscribers: reutskiy.v.v

Differential Revision: https://phab.enlightenment.org/D1681
Genlist: Fix API return value.

elm_genlist_item_subitems_get has to return a list of Elm_Object_Item.
Because of the porting of the genlist item to Eo, this function returns
a list of Elm_Gen_Item.

Thanks to zmike and seoz for catching this.

Fixes T1859
Genlist: Fix previous commit.

The items of an item is a list of Elm_Object_Item and not of Elm_Gen_Item.
Sorry @zmike ;-)

Fixes T1859

Another fix has been added in this commit, related to relative items.
test_slider: Fix wrong slider description.
widget tooltip creation should also pass the eo item to the callback

ref T1859