Implemented Add and AddRange methods

These supplant the static Utilities.Merge() overloads.
Added new WrapperTypes; removed unused code

New WrapperTypes for convenience functions: ConvenienceReturnType to
replace an "out" parameter by a return value, and
ConvenienceArrayReturnType to replace an out array parameter by a
single return value (array count of 1 only).
Add helper overload generation

Functions returning a value or array via an 'out' parameter will now get a convenience overload that returns the result via a return statement. In the case of arrays, only single-valued arrays will be supported. For example:

void GetIntegerv(enum pname, out int value)

will be get an overload of

int GetIntegerv(enum pname)

This will reduce the amount of helper overloads that must be maintained manually in GLHelpers.cs.
Improve indentation for doc comments

Doc comments are now split at their source, as a first step in
normalizing their indentation between VS and MD.
Generate bindings for testing (WIP)
Generate bindings for testing (WIP2)
Corrected indentation
Corrected declarations in convenience overloads
Plural name to singular in convenience overloads
Return types must be cls-compliant

CreateCLSCompliantWrappers must always change return types into
cls-compliant types. The reason is that we cannot overload on return
type alone, so we should always choose the compliant version.
Move convenience overloads to generator

The generator now handles the creation of convenience overloads. These
must be removed from the helper classes to avoid redefinition errors.
Added WrapperTypes.ConvenienceArrayType

These are convenience parameters for function receiving a size and an
array parameter, like DeleteTextures(int n, int[] ids). The generator
will now add overloads taking a single parameter, such as
DeleteTexture(int id).
Restrict convenience overloads

Only Get*, Gen*, Delete* and New* functions get convenience overloads.
This avoids issues with functions such as Rect() that have similar
signatures but cannot use such overloads.

This restriction will be relaxed in the future.
Updated convenience overloads