add linux-x86-power-tools

Dependency of future TLP releases.

There's also sys-apps/linux-misc-apps in the main tree, but it's
(a) outdated and (b) installs the whole suite of tools, e.g. usbip.
app-laptop/tlp-9999: depend on x86_energy_perf_policy
app-laptop/tlp-9999: add optional bluetooth deps

Controlled by the global "bluetooth" USE flag.
app-laptop/tlp-9999: recommend coretemp kconfig
update README
app-laptop/tlp: remove old ebuilds
mask <app-laptop/tlp-0.6 for removal