Fixes to iOS/Android WebHybrid

Fixes calls from an external web page, issue #86.

https://github.com/XForms/Xamarin-Forms-Labs/issues/86
Changed WP8 WebHybrid to support Local call

This will allow the WP8 callbacks to be called with the same redirect
command.
Fixes to the WebHybrid sample

All platforms now update the CanvasJS charts from the native controls.
Added the missing HTML references for WebHybrid
Merge pull request #14 from XForms/master

Merge from main.
#89, changed ImageButton to use a Source property of type ImageSource.
Merge pull request #91 from Bowman74/master

#89, Converted image property to use an ImageSource instead
Json.NET bug fixed, code cleanup

https://github.com/XForms/Xamarin-Forms-Labs/issues/93 fixed. Code
cleaned up to fit into new StyleCop rules.
#28, made documentation changes for StyleCop rules.
Merge pull request #94 from Bowman74/master

#28, made documentation changes for StyleCop rules.
#28, made some changes to be in compliance with StyleCop rules.
#78 Updated front page project info.
Merge pull request #95 from Bowman74/master

#28, made some changes to be in compliance with StyleCop rules.
Hybrid web view screenshots + fixes

The old sample would render CanvasJS fine but would crash as the
JavaScript would create memory leaks. Replaced with JS that does not
cause memory leaks but has some rendering issues on update. It’s not a
C# issue so not a big deal.
Added hybrid view screenshot for iOS
Merge pull request #15 from XForms/master

Merge from main
Made changes to add compilation symbols to android.
Merge pull request #98 from Bowman74/master

Added Android build constant.
Added generic IRestClient interface + JSON client

The client implementation is located in Plugins for the reason that
HttpClient on WP8 requires Microsoft.Http async library and I did not
want to introduce that dependency to all clients. I will try to put in
a ProtoBuf client at some point.

This client implementation depends on the serializer interfaces in the
core project.
Fixing the missed rest client core files