updated lavaca project to v2.3.2
Updated Xamarin assets
Cleaned up Xamarin project files
Updated icons and layout for Window Phone 8 in Xamarin
Added placeholder icon for Android on Xamarin
Updated Xamarin for iOS 7 look and feel

Refs #232
Updated native implementation for iOS 7
Code cleanup for native implementation
Removed unrelated git submodule

Looked like a Sencha Touch 2 git submodule was committed as part of lavaca
work, so is believed to be an accidental / unrelated modification.
Fixed issue preventing lavaca from building

Lavaca has a dependancy on jquery, however it expects that there is an
index.js file.  This is no longer present.

According to Lavaca v2.3.3 the dependency is changed to expect a jquery.js
file, which turns out to be present.

I preferred to apply this fix rather than performing the update to v2.3.3.
Cleaned up cordova build files for lavaca
Updated lavaca assets

Including icons, screenshots and Cordova config files
Merge branch 'master' into lavaca
Updated a few more icons and configs for lavaca
Included images needed by iOS 7 cordova on lavaca
Merge pull request #275 from matthewdunsdon/update-xamarin-for-ios-7-and-wp8

Updated xamarin for ios 7 and Windows Phone 8
Merge pull request #276 from matthewdunsdon/update-native-ios-7

Update native implementation for iOS 7
Merge pull request #277 from matthewdunsdon/lavaca

Prepared lavaca v2.3.2 for PropertyCross