Revert "Added power management support for the Raspberry Pi. Since it doesn't support true standby, we fake it by turning video on or off, and ignoring remote inputs during the standby phase."

This reverts commit 4a8e9bc20c779387cb3e7593c459a1a77de64ad9.
Revert "Added CPowerSyscallVirtualSleep class, which acts as a base class for devices that have no native standby mode, and need to fake it in some way."

This reverts commit 30d266a065beeafc397a3d8067a1e0ae737680d7.
Revert "PowerManager (and its IPowerSyscall instance) now gets called from CApplication::OnKey() and can process and suppress key presses. This is a requirement to implement a virtual sleep state."

This reverts commit 83194ae5afb2bb6f6bd4c46bb615b8f0d2c2199f.