Add Transparent Hugepages option

[eth-p]

This commit adds the ability for PowerTools to change the kernel transparent hugepages setting.

I gave the backend the ability to change between never, madvise, and always, but only gave the frontend the option to toggle between always and madvise. While this might seem like an odd choice, the kernel docs mention that never is "mostly used for debugging purposes". With madvise as the "off" option, it requires processes to explicitly opt in to THP support via syscalls. Presumably these processes would know how to use it properly, and would be negatively affected by turning THP off entirely.

Known Issues:

• Changing the THP enabled setting only affects new processes.
  Depending on how the game launches and the timing of PowerTool's persistence setting, any changes to the THP setting may not take affect in time.

Future Considerations:

• With a new memory section, it might be nice to move the "Downclock Memory" option to there instead of under the GPU section.

[NGnius]

Thanks for the hard work on this! Unfortunately this isn't power-related so I don't think PowerTools is the best fit for THP.

SystemToolbox has support for this, in case you're looking for a plugin that can do this.

Happy Holidays!