Implement AccountManager.removeAccount
Allow specifying manifest, res, and assets via system property.

This is needed when other tooling bootstraps the test running.
Use SimpleFuture for ShadowAsyncTask so `onPostExecute` exceptions are not swallowed

Fixes #686.

`SimpleFuture` provides a very basic implementation of the necessary functionality for ShadowAsyncTask and doesn't swallow
exceptions in the same way that `FutureTask` does. It is a little weird as it doesn't allow cancellation while running but it
seemed overkill to add this functionality as Robolectric is single threaded.
Make sure that `onPostExecute` exceptions are differentiated from `doInBackground` exceptions if `onPostExecute` runs synchronously
Reformat `ShadowAsyncTask`
Merge pull request #697 from coreydowning/async-future-rewrite

Stop ShadowAsyncTask swallowing exceptions in `onPostExecute`
`ShadowAsyncTask#executeOnExecutor` runs on the passed `Executor`.
Reformat `ShadowAsyncTask` and `AsyncTaskTest` to match code style.
Fixed path separator in PackageResourceLoader.java
Merge pull request #699 from SuperJugy/pathSeparatorFix

Fixed path separator in PackageResourceLoader.java
Add option for startActivity to throw ActivityNotFoundException when Activity is not in the PackageManager.
Add Activities in the AppManifest to the application's PackageManager in default test lifecycle
Add static helper to Robolectric for configuring Activity checking
Fix File.separator issues in tests
Consider android maps and play services classes to be part of the Android SDK, but other classes under com.google.android to not be.
Merge pull request #702 from SuperJugy/FileSeparatorFixes

Fix File.separator issues in tests
Merge pull request #706 from erichaugh/master

Consider android maps and play services classes to be part of the Android SDK, but other classes under com.google.android to not be.
Correct StatFs tests to use absolute path so they will pass on other platforms (test was assuming Unix absolute paths)
Remove PhoneNumberUtilsTest because it's just testing real android code and will fail in many non-US locales.
Merge pull request #709 from coreydowning/remove-phone-number-utils-test

Remove PhoneNumberUtilsTest