BMC adapter support.

[yixingjia]

With BMC(Baseboard management controller) we can get a lot of useful metrics of a server. Currently we still not have this adapter ready.

There are two cases.

1. The user has a BMC management system. in this case we can extract data directly from the BMC management system directly which is more easier.

2. The use don't have BMC management system, instead the adapter need to connect directly to the BMC on the motherboard. In that case. we need to create a simple UI for the BMC connection management. Beside that there are different type of BMC implementation from different vendors. We need to address which we will support in the first version.