Issue 4028 - Add support for Edge extensions to buildtools

docs/metadata.edge.example

 [default]
 # Base metadata file whose sections and keys we inherit but can override.
 inherit = metadata.common
-
-# App identity assigned by the Windows Dev Center.
-[package_identity]
-name = ACME.MyExt
-publisher = CN=4F066043-8AFE-41C9-B762-6C15E77E3F88
 
 # Icons to be placed into /Assets and referenced in AppxManifest.xml.
 [appx_assets]
 # 50x50 logo for the store.
 logo_50.png = path/to/logo_50.png
 
 # 44x44 and 150x150 logos for Windows UI.
 logo_44.png = path/to/logo_44.png
 logo_150.png = path/to/big_logo.png
 
 [compat]
-# Target Edge version.
+# Target Edge version (for manifest.json)
 edge = 37.14332.1000.0

[Sebastian Noack, 2016/07/11 16:29:44]

would this actually be used? It seems we only have min/max "windows" versions in
the generated AppxMainfest.xml? (In test/metadata.edge you specify both)

[Vasily Kuznetsov, 2016/07/12 09:38:08]

This end up in `minimum_edge_version` key in `manifest.json` inside of
`Extension` folder. That's how it is in the example extension that you provided
me with.

However, min/max Windows versions should be documented here, so I added that.

+# Min/max windows version (for AppxManifest.xml)
+windows = 10.0.14332.0/12.0.0.0
 
 [general]
+# App identity and publisher ID assigned by the Windows Dev Center.
+app_id = ACME.MyExt
+publisher_id = CN=4F066043-8AFE-41C9-B762-6C15E77E3F88
+
 # Base name of the plugin file (version and extension will be added to this).
 basename = myext-edge
 
-# Display name and description for the manifest files.
-display_name = MyExt
-description = MyExt is the greatest extension
-
 # Background color for the Appx manifest.
 background_color = pink
-
-# Extension ID for Appx manifest.
-extension_id = 1.0
 
 # Permissions of the extension to place into manifest.json
 # (see https://developer.chrome.com/extensions/declare_permissions).
 permissions =
   tabs
   bookmarks
   http://*/*
   https://*/*
 
 # UI definitions.
 options = options.html
-devtools = devtools.html
 
 # Icon for the browser toolbar. Used to produce browser_action key in
 # manifest.json (see https://developer.chrome.com/extensions/browserAction).
 browserAction = icons/icon-19.png icons/icon-38.png popup.html
 
 # Icons for manifest.json.
 icons = icon-16.png icon-32.png icon-48.png icon-64.png icon-128.png
 
-# Schema for managed storage (storage.managed_schema in manifest.json).
-managedStorageSchema = schema.json
-
-# Files that are renamed/moved when placed into the package. 
+# Files that are renamed/moved when placed into the package.
 [mapping]
 target/path/file.png = source/path/icon.png
 
 # Javascript source files to be compiled/bundled by JSHydra.
 [convert_js]
 # Two files bundled into one.
 path/bundle.js = source/path/src1.js src2.js
 
 # Remove a file from a bundle defined in common.metadata.
 path/common-bundle.js -= removed/src.js