rpcclient: update documentation, mention subpackages

Drop TODOs (we have relevant GitHub issues), drop verbosity comment (we have
*Verbose APIs for that).

pkg/rpcclient/doc.go

@@ -1,21 +1,57 @@
 /*
 Package rpcclient implements NEO-specific JSON-RPC 2.0 client.
-This package is currently in beta and is subject to change.
+
+This package itself is designed to be a thin layer on top of the regular JSON-RPC
+interface provided by Neo implementations. Therefore the set of methods provided
+by clients is exactly the same as available from servers and they use data types
+that directly correspond to JSON data exchanged. While this is the most powerful
+and direct interface, it at the same time is not very convenient for many
+purposes, like the most popular one --- performing test invocations and
+creating/sending transactions that will do something to the chain. Please check
+subpackages for more convenient APIs.
+
+# Subpackages
+
+The overall structure can be seen as a number of layers built on top of rpcclient
+and on top of each other with each package and each layer solving different
+problems.
+
+These layers are:
+
+  - Basic RPC API, rpcclient package itself.
+
+  - Generic invocation/transaction API represented by invoker, unwrap (auxiliary,
+    but very convenient) and actor packages. These allow to perform test
+    invocations with plain Go types, use historic states for these invocations,
+    get the execution results from reader functions and create/send transactions
+    that change something on-chain.
+
+  - Standard-specific wrappers that are implemented in nep11 and nep17 packages
+    (with common methods in neptoken). They implement the respective NEP-11 and
+    NEP-17 APIs both for safe (read-only) and state-changing methods. Safe methods
+    require an Invoker to be called, while Actor is used to create/send
+    transactions.
+
+  - Contract-specific wrappers for native contracts that include management, gas,
+    neo, oracle, policy and rolemgmt packages for the respective native contracts.
+    Complete contract functionality is exposed (reusing nep17 package for gas and
+    neo).
+
+  - Notary actor and contract, a bit special since it's a NeoGo protocol
+    extension, but notary package provides both the notary native contract wrapper
+    and a notary-specific actor implementation that allows to easily wrap any
+    transaction into a notary request.
+
+  - Non-native contract-specific wrappers, currently partially provided only for
+    NNS contract (it's still in development), at the moment that's mostly an
+    example of how contract-specific wrappers can be built for other dApps
+    (reusing invoker/actor layers it's pretty easy).
 
 # Client
 
 After creating a client instance with or without a ClientConfig
 you can interact with the NEO blockchain by its exposed methods.
 
-Some of the methods also allow to pass a verbose bool. This will
-return a more pretty printed response from the server instead of
-a raw hex string.
-
-TODO:
-
-	Allow client to connect using client cert.
-	More in-depth examples.
-
 Supported methods
 
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