RPC - Add getbestchainlock (#160)

* RPC - Add getbestchainlock

* Add missing markdown file

_includes/devdoc/dash-core/rpcs/quick-reference.md

@@ -117,6 +117,7 @@ These RPCs are all Dash-specific and not found in Bitcoin Core
 {% autocrossref %}
 
 * [GetBestBlockHash][rpc getbestblockhash]: {{summary_getBestBlockHash}}
+* [GetBestChainLock][rpc getbestchainlock]: {{summary_getBestChainLock}} {{DASH_NEW0_14_1}}
 * [GetBlock][rpc getblock]: {{summary_getBlock}} {{DASH_UPDATED0_14_1}}
 * [GetBlockChainInfo][rpc getblockchaininfo]: {{summary_getBlockChainInfo}} {{DASH_UPDATED0_14_1}}
 * [GetBlockCount][rpc getblockcount]: {{summary_getBlockCount}}

_includes/devdoc/dash-core/rpcs/rpcs/getbestchainlock.md

@@ -0,0 +1,64 @@
+{% comment %}
+This file is licensed under the MIT License (MIT) available on
+http://opensource.org/licenses/MIT.
+{% endcomment %}
+{% assign filename="_includes/devdoc/dash-core/rpcs/rpcs/getbestchainlock.md" %}
+
+<!--__-->
+
+##### GetBestChainLock
+{% include helpers/subhead-links.md %}
+
+{% assign summary_getBestChainLock="returns the block hash of the best chainlock." %}
+
+{% autocrossref %}
+
+The `getbestchainlock` RPC {{summary_getBestChainLock}}
+
+Throws an error if there is no known chainlock yet.
+
+*Parameters: none*
+
+*Result*
+
+{% itemplate ntpd1 %}
+- n: "`result`"
+  t: "object/null"
+  p: "Required<br>(exactly 1)"
+  d: "An object containing the requested block, or JSON `null` if an error occurred"
+
+- n: "→<br>`blockhash`"
+  t: "string (hex)"
+  p: "Required<br>(exactly 1)"
+  d: "The hash of the block encoded as hex in RPC byte order."
+
+- n: "→<br>`height`"
+  t: "number (int)"
+  p: "Required<br>(exactly 1)"
+  d: "The height of this block on its block chain"
+
+- n: "→<br>`known_block`"
+  t: "boolean"
+  p: "Required<br>(exactly 1)"
+  d: "True if the block is known by this node"
+
+{% enditemplate %}
+
+*Example from Dash Core 0.14.1*
+
+{% highlight bash %}
+dash-cli -testnet getbestchainlock
+{% endhighlight %}
+
+Result:
+{% highlight json %}
+{
+  "blockhash": "000000000036ab34d3005941d4224fc5887526355c98b769e27e5ece05f48860",
+  "height": 182106,
+  "known_block": true
+}
+{% endhighlight %}
+
+*See also: none*
+
+{% endautocrossref %}