Move core services into their own module

[tomwayson]

Created esri.core module as a dependency of esri.map.
Added a test page to demonstrate using the core module to define your own directive.

[tomwayson]

Resolves #69

@jwasil please review, specifically:

• Did I get the breakdown right in terms of what is/isn't in core?
• Layer controllers extending a base controller - I'm not super stoked on this, but it's working. Kinda goes back to what @mpriour suggested a long time ago - should just be one layer directive w/ a type attribute ("feature", "dynamic", etc). Extending a base controller seems like a compromise that let's us keep our current directive API
• Folder structure, file naming, etc. This should be the final API for 1.0, so let's make sure it's right.
• I don't think the sample I used for the custom directive test page makes for the best demo of a custom directive (doesn't have any bound attributes).I wanted to use the raster slider example, but I didn't want to deal w/ getting an angular slider (this one seems like the best non-UI framework one) working w/ it (it was late). I'm open to suggestions for other samples, or one of us could give the raster slider a go, but probably after merging and under a new issue.

[jwasilgeo]

Wonderful work here! Great updates through and through.

• Breakdown of core and non-core: yeah!
• Shared base layer controller: I modified the bindLayerEvents method a bit so that non-shared event bindings could move out of link and up into the layer-specific controller files.
• Folder structure: I know we're not really in the business of providing dijit wrappers in this repo, but should the esriLegend be moved to a new folder other than "map"?
• New example for custom directive: nice! BlendRenderer is cool to see. I added some bindings for basemap and layer visibility. And yes raster slider would be great--let's plan on doing that in another issue--would be a good showcase of JSAPI functionality regardless of framework.
• Housekeeping for TODO comments in src that we haven't explicitly discussed in awhile:
  • I think layerInfo is fine according to JSAPI docs, but I just added a Number conversion to hideLayers.
  • esriMapUtils.createWebMap: I agree, not having to pass mapController would be nice, but seems tricky to solve right now.
  • TimeExtent and other nice-to-haves for dynamic layer in esriLayerUtils: Yeah, for this PR seems totally fine; do we want to put in issues for another RC later down the road?

Thoughts on above items or what was pushed in 217e818, @tomwayson?

[tomwayson]

@jwasil thanks for the thorough review. I like your additions and have merged them (after a few minor changes to names and wording).

Thoughts:

• we'll leave out the "nice to haves" from the API at this point. Just need to remember to document the unsupported dynamic map service layer options when writing docs.
• I had the same thought about a folder for esriLegend. I don't even know what I would call the folder for esri/dijit type directives. Sure as hell not "dijit." Let's leave it under map for now.

The v.1 API is now complete! Let's add some tests, docs, and put a bow on this thing.