[App] Fixed behavior on Proxy screen

[philips77]

This PR fixes some issues on the Proxy tab.

[philips77]

Fixed issues:

• [x] #589
• [x] Disconnecting proxy works
• [x] Switching to another proxy node works
• [x] A popup with a warning is shown when max size of Proxy Filter list is reached

Breaking:

1. In ProxyFilterDelegate:

   limitedProxyFilterDetected(maxSize: Int)

   was replaced by

   proxyFilterLimitReached(type: ProxyFilerType, maxSize: UInt16)

   The former is now deprecated.

[philips77]

Other changes:

1. In ProxyFilterDelegate the

   proxyFilterUpdated(type: ProxyFilerType, addresses: Set<Address>)

   is now called after the list size has been acknowledged. It is always called before

   proxyFilterUpdateAcknowledged(type: ProxyFilerType, listSize: UInt16)

   or

   proxyFilterLimitReached(type: ProxyFilerType, maxSize: UInt16)

2. These methods are called after calling proxyDidDisconnect().