Add errors and assertions to Acc computations

[ivogabe]

Description

This PR adds throwing errors and assertions to Acc computations. See AccelerateHS/accelerate#494

Motivation and context

These functions should make it easier for users to detect problems in their code. It is also possible to use these functions for parts of the algorithm which haven't been implemented, similar to undefined from the Prelude, as the program now still compiles and will only crash when such part is actually used.

How has this been tested?

Just a quick test, no automated tests yet.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.