Add Abs, Dot and AbsDot and respective tests to Vector4

[luccosta]

Resolves #71 .

This implements the functions Abs(), Dot(Vector4) and AbsDot(Vector4) in Vector4 API, similar to the existing same functions in Vector3.

It enables Vector4 objects to perform:

vec4.Abs();
vec4_a.Dot(vec4_b);
vec4_a.AbsDot(vec4_b);

Did all checks and tests.

[luccosta]

After merge ign-math6 backwards, locally everything is running ok, but the Ubuntu Bionic CI is getting:

Unexpected input(s) 'script-after-make', valid inputs are ['entryPoint', 'args', 'github_token', 'apt-dependencies', 'codecov-token', 'cmake-args']

And I'm not finding anything about this.

Same happening on ruby PR #137 .

[chapulina]

Unexpected input(s) 'script-after-make'

Don't worry, you can ignore this. It's a problem with our infrastructure.