Add lg_navlib package

[mvollrath]

Backend support for lg_navlib user interface library.

The nav_mode.py script listens for application state changes and publishes configured navigation mode when applications become visible.

The intention is to help user interfaces send appropriate axis translations for the panoramic content.

For example, the SpaceNav axes are different between:

• Globe apps like Cesium and Earth
• Eye-level apps like Street View and panoramic image/video

When implementing a generic multi-touch to SpaceNav interface, we need to know which axis mapping to use. Pan may be translation in one context and rotation in another.

[sourcelevel-bot[bot]]

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• 2 possible new issues (including those that may have been commented here).

But beware that this branch is 27 commits behind the EndPointCorp:master branch, and a review of an up to date branch would produce more accurate results.

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