Misc fixes

[9prady9]

Change(s)

1. CMake Fixes
2. Helper header (ComputeCopy.h) file rename

Current Behavior

1. CMake Warnings
2. Name-Conflict errors on user system with another header with same (ComputeCopy.h) name.

New Behavior

1. No Warnings
2. No name conflicts

Breaking Change(s)

1. Name/Location change of ComputeCopy.h header to fg/compute_copy.h

Please check if the PR fulfills these requirements

• [x] The commit message following the guidelines
• [x] Examples for all compute backends, CUDA & OpenCL, have been added/modified accordingly
• [x] Docs have been added / updated (for bug fixes / features)