Added Power On Command to SystemControl

[alliefitter]

Borrowed wake on lan functionality from LGWebOSRemote. klattimer was running arp with Popen in order to get the TV's MAC address. I just added a dependency which is pure Python.

[coveralls]

Coverage decreased (-0.3%) to 84.543% when pulling 6aa2bbdfa838e26e654a70962a788a10945235ed on alliefitter:power-on into c6236e599645d14626c4d15fad56eac9f4cbacd2 on supersaiyanmode:master.

[alliefitter]

@supersaiyanmode After playing around with the CLI I've been building, I've run into some issues using this feature. Namely, having this is as an instance method of a control requires that the client connect which is pretty hard to do when the TVs not on (which is also very obvious hindsight, lol.). After our discussion on #24 about the "agents," it seems pretty clear that you want this package to be an API interface/SDK and that you don't want to shove functionality into it. Correct me if I'm wrong, but if I'm not, you can go ahead an close this PR. I'm just going to add power on functionality to the CLI.

[supersaiyanmode]

There were several reasons why I was always a hesitant about adding WOL into this library.

• Once you you have the hostname from the discovery, everything that goes into being able to wake up the TV through WOL has nothing to do with the (WebSocket based) interface this library provides.
• It should probably be out of all WebOsControl classes (It should perhaps be something like: pywebostv.utils.power_on(host_name)). This would then be the only API in the utils module, and unless there are others, adding WOL means adding a new dependency to the project.
  • As you figured out, a power_on is pretty useless when there's an active connection object ie TV is awake. We need a mechanism to save the IP address or MAC address for later use -- something that is out of scope for this library.
• If the consumer of the library does this, it's literally two lines of additional code.

But pros:

• Everything you'd ever need is packaged in one single library. This is a huge win for many folks.

This makes it difficult for me to decide ...