Remove portbin from docs for now

fix minor text issues in compile.md

instructions for new gcc versions

Yet another nicehash workaround -.-

Add filename to backend errors

New thumbnail

POW AEON v7

- documentation: change `aeon` to `aeon7`
- change `case` order in `switch` statements
- update README.txt

add cli option `--noAMDCache`

allow to disable the OpenCl cache
  - usefull for read only systems
  - usefull for unknown errors during cache reading

fix parentheses warning

documentation: name a worker

fix autoAdjust(non hwloc)

fix warning

```
/Users/user/xmr-stak/xmrstak/backend/amd/amd_gpu/gpu.cpp:481:11: warning: using the result of an assignment as a condition without parentheses [-Wparentheses]
                if( ret = clGetProgramInfo(ctx->Program, CL_PROGRAM_BINARIES, num_devices * sizeof(char*), all_programs.data(),NULL) != CL_SUCCESS)
```

add note that `rig_id` is ignored by some pools

- add new pow for AEON
- fix missing cryptonight-heavy selection for multi hashes

- add tests whith disabled dependencies

- remove call `IsCurrencyMonero` with `cn_select_memory`

reenable MACOSX travis tests

remove old release signatures

the signatures for the next release will be in the release note itself

Change video guide to a placeholder link

rename `monero2` to `monero7`

fixAMD benchmark mode

revert input size change

fix #1202

move option currency down

revert #1198, the block size is limited to 84byte

move option `--currency` down

OpenCL precompiled code message

increase version to 2.3.0

The OpenCl code is only supporting jobs up to 84byte

change warning when precompiled OpenCL code is not found