Cleanup CCEffectImpl's initialization flow

This is yet another CCEffects cleanup change in preparation for Metal support. It's pretty big but for the most part reviewers can focus on the changes to CCEffect_Private.h and CCEffect.m. The remainder of the changes are sub-classes adapting to the super-class modifications.

- Simplify CCEffectImpl initialization flow. Prior to this change, an effect subclass called one of several initializers on CCEffectImpl of the form:

```
initWithArg:arg
initWithArg:arg blarg:blarg
initWithArg:arg blarg:blarg flarg:flarg
```

Which all chained to initWithArg: blarg: flarg:. The designated initializer then did the following:

```
if (!arg) [self buildArg];
if (!blarg) [self buildBlarg];
if (!flarg) [self buildFlarg];
```

And sub-classes could opt to override these builder methods. This change removes the overridable builder methods and, for the most part, requires the sub-classes to supply all components (functions, uniforms, varyings, etc) at the time that the super-class initializer is called.

This makes the super-class initializer call more verbose but it makes the overall flow more straightforward. It also addresses potential initialization order problems with overridden builder methods being called on the sub-class before the sub-class's initializer body could execute.

- The function, uniform, and varying arrays are now readonly to prevent them being modified after initialization.

- CCEffectImpl's self pointer is no longer captured by the render pass blocks. Instead the blocks capture the interface class that owns the CCEffectImpl which prevents capturing self before super-class initialization is complete (which is what we were doing before).

- Move some setup code that was duplicated between blur, bloom, and drop shadow into a shared function.