readd nicehash pool support

use nicehash start nonce in all backends if nicehash is enabled

fix donation section

refactor xmr-stak

- add CIvariables to debug cuda build

- fix windows CI
- add CUDA to linux CI

- add more documentation
- split documentation into different files

- string literal can only be 16kbyte

- add clang compile section
- cleanup CMake file
- fix missing return value

- add pseudo install rule to CMake

- 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`

- executor.h: expose log_`result_error()`
- register wrong results

- create config on startup
- remove copy `config.txt` on `make install`

Use command line poolname, password and username  if defined

- splitt literal to smaller chunks (windows only support 16k literals)
- remove copy command for opencl folder

- store most importend parameter in a singleton
- use config file parameter

- inlcude opencl source code during compile

- amd/nvidia add hard limit that 64MiB memory keeps free
- improve nvidia auto suggestion (take care of lmem)
- add c++11 flag to nvidia compiler

- add excecutor to the singleton export list

- pass all singletons into the backend libraries
- move some cpu config features from the cpu config file to the global config.txt
- add global jconf to the xported singleton list

- fix build documentation
- fix plugin load methods
- fix symbol export for plugins

- add `CUDA_ENABLE`
- add `OpenCL_ENABLE`