Add local saving of wakewords option

[el-tocino]

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Allow wakewords to be saved locally.

Be clear about the software, hardware and version you are running

• I'm running precise
• With version 18.8
• With custom wake words.

Try to provide steps that we can use to replicate the Issue

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Be as specific as possible about the expected condition, and the deviation from expected condition.

Currently, if enabled, wakewords are uploaded to training.mycroft.ai. If you do custom precise models, it would be helpful to have local copies of these saved for additional training. This could be used to help refine against false positives and improve relevant mic input recognition. This is an advanced option, I'd be very ok with it as a local mycroft.conf setting.

see also MycroftAI/mycroft-precise#53

Provide log files or other output to help us see the error

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Upload any files to the Issue that will be useful in helping us to investigate

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[el-tocino]

Closing per #2141 2141