Get thumbnail from app (#68)

* Renamed multipart filed name 'files' to 'assetData'. 
* Added an additional field name of 'thumbnailData' to multipart form.
* Implemented upload mechanism for thumbnail directly from the mobile client.
* Removed dead code
* Implemented a version checking mechanism.

mobile/ios/fastlane/Fastfile

@@ -18,6 +18,9 @@ default_platform(:ios)
 platform :ios do
   desc "iOS deployment"
   lane :beta do
+    increment_version_number(
+      version_number: "1.3.0" # Set a specific version number
+    )
     increment_build_number({
       build_number: latest_testflight_build_number + 1
     })