Assert messages improved.
Added some special case error hint messages to help locate the cause for an assert.
Merge pull request #747 from NickyWeber/feature/sb#360_improved_assert_messages_in_ccbreader

Assert messages improved.
Ordering of nodes in a CCLayout depends on children's z-order which is now correct after adding a node.
Fixes the SpriteBuilder bug #465.
Merge pull request #753 from NickyWeber/bugfix/sb#465_cclayoutbox_spritebuilder

Ordering of nodes in a CCLayout depends on children's z-order which is n...
CCNodeGradientRadial: Quick radial gradient using GL_TRIANGLE_FAN

CCNodeGradientRadial draws radial gradient just as
CCNodeGradient draws a linear gradient over a quad.

CCNodeGradientRadial offers a lot of control over how the gradient
should look using startColor, endColor and gradientFactor properties.

Performance wise it should be much faster than creating a radial
gradient using a fragment shader or using a texture. Also, since it
uses native gl draw call, it should save a lot in terms of assets.

At present CCNodeGradientRadial uses 14 vertex per quad to
create a gradient. But, it can be increased/decreased by changing the
value stored at macro kCCNodeGradientRadialResolution.

CCNodeGradientRadial is not an extension of CCNodeColor or
CCNodeGradient as might seem at first look. But interface-wise
it is very similar to CCNodeGradient.

The two main reasons are:

1. CCNodeColor only has 4 vertex available whereas for a
gradient we certainly need more than that.

2. CCNodeColor uses GL_TRIANGLE_STRIP for rendering whereas
CCNodeGradientRadial uses GL_TRIANGLE_FAN
Add comments for CCNodeGradientRadial class
Merge branch 'master' into develop

Conflicts:
	cocos2d-ui/CCBReader/CCBReader.m