Add gmf feature style directive

[adube]

This PR introduces a gmf-featurestyle directive and an example featuring it. It also introduces a gmf.FeatureHelper service that is responsible of giving utility methods to create, get and set the style for a feature using its inner properties. It also contains methods to calculate and return a measure string from a feature geometry.

Wiki: https://github.com/camptocamp/c2cgeoportal/wiki/Spec-%231658-Measures-and-redlining

Tasks remaining to do

• Deal with circle measurements, i.e. how should we do it properly. If we do not support ol.geom.Circle as type of geometry, then we need to adjust what has been made. Answer: we'll keep circles as polygons, as before.
• Travis build pass
• Code review

Live example

• http://adube.github.io/ngeo/edit-feature-style/examples/contribs/gmf/featurestyle.html?map_x=-8003263&map_y=6362007&map_zoom=6

[adube]

@fgravin Ready for review.

[pgiraud]

@adube Let's forget about the "icon" that was supposed to be displayed ahead of measure. I don't this is required. Can you please remove the bordered text in you example?

[fgravin]

Code could be a bit factored.

[gmf.FeatureProperties.ANGLE, gmf.FeatureProperties.COLOR, ...].forEach(function(propName) {
keys.push(
         ol.events.listen(
             newFeature,
             ol.Object.getChangeEventType(propName),
             this.handleFeatureChange_,
             this
         )
     );
}.bind(this)

[fgravin]

Looks good in the approach.
Maybe worth it to improve the css (slider etc..), it's gonna be usefull for desktop integration.

Have you watched the FeatureHash format ?
https://github.com/camptocamp/ngeo/blob/master/src/ol-ext/format/featurehash.js
It does parse and serialize styles from/to properties, you need to have a look and be sure everything is coherant and no code is duplicated. Thanks.

[adube]

• removal of "icon": OK
• improve css: OK (for slider, for the rest it's already fine, I think)
• FeatureHash: I'll need to discuss this more with you, @fgravin.

[adube]

@fgravin I made all the requested/discussed modifications, with the exception of the modifications to the FeatureHash. It will be easier to make those fixes when we implement the Permalink with it, in an other PR.

Please merge if everything looks okay (once Travis passes).

[adube]

(You may need to clean your browser cache to see the changes in the live example).

[fgravin]

shouldn' start with upper case, it's not a class

[adube]

I'll fix this. Sorry, I'm used to OL3 doing it this way, see: https://github.com/openlayers/ol3/blob/master/src/ol/layer/layerbase.js#L12

[fgravin]

Well maybe i'm wrong ..

[fgravin]

keep it like this then.

[tsauerwein]

For enums upper-case is fine. 👍

[adube]

Thanks for the review.