wrlib: merge gradient duplicate code

This patch is adding a new static function named renderGradientWidth
to factorize some code.
wmaker: update NEWS for 0.95.6
WPrefs: set default to 1st color in gradient texture

This patch is updating the gradient texture user experience
by auto selecting the first color in the list when possible
and fixing the autoselection after a delete action.

In fact what that is called gradient colors is just a list of colors
with hue/saturation/brightness value.
That patch is loading the first one from the list (color, hue,
saturation, brightness) and setting the 3 sliders according to that
value instead of using some default hardcoded values.
The default color value on the top-right is never modified.
wmaker: fix focused window list order

This patch is fixing the focused next window list order.
As now, the switching was only working for 2 windows.
For example, taking 3 windows called A,B,C.
If the windows list is A,B,C where A is the current focused window.
Focusing on B will result on switching position A and B, thus C will
never be the next window.
For this example the patch is updating the linked list as B,C,A.
wmaker: add next and previous window focus functions

This patch is adding a wWindowFocusPrev() and wWindowFocusNext() functions.
And copying switchmenu.c focusWindow() as wWindowSingleFocus().
wmaker: use defined wWindowSingleFocus() function

This patch is cleaning focuswindow() local function to call
wWindowSingleFocus() global function.
wmaker: add new button and wheel mouse actions

This patch is adding atomic mouse actions to mouse buttons to:
-focus on previous or next window
-move to previous or next workspace

and adding wheel action to
-switch between windows
WPrefs: add new mouse actions configuration

This patch is adding GUI configuration for new mouse actions:
-Previous Workspace
-Next Workspace
-Previous Window
-Next Window
-Switch Windows
wmaker: Remove dead links from BUGFORM.
Import git snapshot version 0.95.6+20140912.
debian/control: Add Replaces and Breaks for wmaker-ubuntu-themes and
wmaker-unity-greeter-badge.  Both were old ppa packages now incorporated in
wmaker-common.
debian/README.ppa:  Remove notes above removing wmaker-ubuntu-themes and
wmaker-unity-greeter-badge, as removal will now be taken care of by dpkg.
debian/changelog: Update for version 0.95.6+20140912-1.