fix nicehash `invalid results`

OpenCL: avoid out of memory access

During the initialization of the compile parameter for OpenCL it could be that the
fixed size buffer is to small. To avoid this we are now using `std::string`.
There is no problem by using `std::string` because this part of code is not perfromance critical.

If the first bit of the nonce is `1` (this is very often if we use a nicehash pool)
than it could be that some OpenCL implementations handle the 64bit representation of the 32bit
nonce on the device side as signed integer.
During a right bitshift we pull wrong ones from the wrong higher part of the 64bit
nonce representation into the 32bit part of the nonce.
The result will be that the computed share is invalid.

- explicit cast the nonce on the device to `uint` to avoid any side effects

Update `doc/FAQ.md` with unified proper methods for Linux limits

unify cpu cryptonight implementations

xmr-stak has several implementations for multi hash per thread.
The results into 3 intepedent implementations.
Each time the algorithm must be changed the possibility to introduce errors is very large.

- unify the different cryptonight CPU implementations
- simplify the function selection array to find the specilized cryptonight implementation
- add a intermediat pointer to access the large state (similar to the old multi hash implementation)

As side effect this change increases the speed of the single and multi hash algorithm.

add self test hashes

The most algorithm currently are not checked in the cpu self test function.

- add hash for each algorithm

Add detail to CUDA detections, better for issue reports

Download Link for AMD APP SDK 3.0 fixed

Incorrect Grammar fix

Improve the grammar of the Dev donation setting.

Docs - compilation RAM requirements

Grammar Fixes

Dev

adding qrl as a config option

Fix Spelling

changed chose to choose

release 2.4.7

increase version to 2.4.7

remove countype from version number

fix broken OpenCL 1.2 support

The coint type was set to a fixed value in one of the last released and has no meaning since we support many cryptonight coins.

- remove cointtype from version.cpp

OpenCl 1.2.is not allowing the subscript operator on buildin vector types.

fix: use `.sX` to access vector components

release 2.4.6

increase version to 2.4.6

cryptonight_bittube2

5% more hash per second

Grammar fixes; mmap alloc failed error remark for Arch Linux.

WebUI Relative Links

- add cryptonight_heavy derivate cryptonight_bittube2
- add coin bittube
- remove coin ipbc because this coin is now called bittube

Buffer output in each line