add option `unroll` for OpenCL to allow better tuning the main POW kernel.

fix double definition of define `MEM_CHUNK`

- add new option `comp_mode` to the amd config
- disable `if guards` within opencl kernel if `comp_mode : false`

- add new option for `strided_index`
- add additional option if `strided_index == 2` to controll the memory chunk with

Change the default for strided index. Th euser feedback shows that strided_index = true will give a view hashes more per second.

Allow to change the indexing used to address the hash scratchpad memory.

- add option `strided_index` for each gpu

- move source code to `src`
- categorize files and move to group folder
- change upper case class files to lower case
- change C++ header to `*.hpp`

- add backend
- add auto suggestion