design the uniform standard for device configuration

Currently arguments for `config_board` method are device specific and determined by device manufactorer. For some devices we've added custom commands like: `board.config_board("sampling_rate:500")` but it's also not unified.

Need to take a look at all these commands and design uniform format for it in user API. Behind the scene these format will be converted to device-specific commands.

Types of commands we currently have:
* Muse boards preset commands (p50, p61,etc)
* OpenBCI Cyton (x12345678X)
* Ant Neuro (sampling_rate:500)