Add setting for selecting automatic lpm ui triggering modes

Previously both "from-pocket" and "hover-over" proximity triggering
was enabled implicitly when use_low_power_mode setting was enabled.
The proximity sensor interaction needed for "hover-over" triggering
can be confusing and disabling it was not possible.

Now both triggering types can be disabled/enabled individually via
mcetool - for example:
* only "from-pocket"
  mcetool --set-lpmui-triggering=from-pocket
* both "from-pocket" and "hover-over"
  mcetool --set-lpmui-triggering=from-pocket,hover-over
* neither
  mcetool --set-lpmui-triggering=disabled

Default is to enable "from-pocket" only.

[mce] Add setting for selecting automatic lpm ui triggering modes. Fixes JB#20959
Fix indentation
Merge pull request #205 from spiiroin/lpm_triggering_setting

Add setting for selecting automatic lpm ui triggering modes