Option to use Broker and configurable redirect URL

[BeMor81]

Copied over definitions for index.d.ts as importing caused issues unless both ios and Android development environments were setup.
Storing userId persistently in Android for use with subsequent requests. Corrected the scope of "this" on Android login success.
initContext() was created as initialising in the constructor created lengthy startup times within app when utilised by a service.
Add the option to set Broker as true so to utilise Broker apps such as Company Portal for Android and Authenticator for iOS. The latter requires different bespoke redirect URLs for each platform so hence the introduction of MultiPlatformRedirectUri. For further information on what the redirect URLs should be and further app settings required please read the documentation below.

https://docs.microsoft.com/en-us/azure/active-directory/develop/active-directory-sso-android
https://docs.microsoft.com/en-us/azure/active-directory/develop/active-directory-sso-ios

[YvesCandel]

Hi @BeMor81 , thanks for your contribution. I'll give your PR a quick test soon!