Deprecate/refactor content in docs/specification (#1934)

* docs: deprecate specification dir, closes #1814

* update genesis

* old spec dir, deprecation complete

* rm a file

docs/tendermint-core/light-client-protocol.md

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+# Light Client Protocol
+
+Light clients are an important part of the complete blockchain system
+for most applications. Tendermint provides unique speed and security
+properties for light client applications.
+
+See our [lite
+package](https://godoc.org/github.com/tendermint/tendermint/lite).
+
+## Overview
+
+The objective of the light client protocol is to get a
+[commit](./validators.md#committing-a-block) for a recent [block
+hash](../spec/consensus/consensus.md.md#block-hash) where the commit includes a
+majority of signatures from the last known validator set. From there,
+all the application state is verifiable with [merkle
+proofs](./merkle.md#iavl-tree).
+
+## Properties
+
+-   You get the full collateralized security benefits of Tendermint; No
+    need to wait for confirmations.
+-   You get the full speed benefits of Tendermint; transactions
+    commit instantly.
+-   You can get the most recent version of the application state
+    non-interactively (without committing anything to the blockchain).
+    For example, this means that you can get the most recent value of a
+    name from the name-registry without worrying about fork censorship
+    attacks, without posting a commit and waiting for confirmations.
+    It's fast, secure, and free!