Beta 5

This 5th beta improves stability a lot, including in the use of threads.

Changelog:

• Updated sample and README to provide an easy-to-run example on how to signIn and getDialogs
• Moved all parameters common parameters of same type constructors into the abstraction superclass for more convenience (avoid having to cast each time)
• Forced UTF-8 usage when converting strings from/to bytes
• Now automatically handles FILE_MIGRATE_X error when downloading a file, a new connection to the appropriate DC will be created and the request will be executed there (this case may add some additional delay)
• Completely removed the "reactive client" for now
• Improve thread usage/cleaning after usage
• Added method to change your client's timeout
• Fixed some bad connection to Telegram by using a "retry policy" which will close the bad socket, and open a new one to retry once
• Refactored TLContext class to fix various bugs related to serialization/deserialization
• Refactored methods taking a TLVector<> as an argument to accept a covariant version. It'll be useful for example when taking a TLVector<TLAbsInput> you can now give a TLVector<TLInputUser>
• Added convenience methods to get cast version of object if the type has only 2 constructors, and one of them is an "empty" type constructor (ie: TLAbsUser has TLUser and TLUserEmpty constructors). You can just call isEmpty() or getAsUser() in this case