lnrpc: add cursory REST support to the RPC server

This commit adds a REST interface to the existing gRPC server by
employing a simple http proxy auto-generated from the existing protobuf
files. Currently full-support for any streaming RPC’s are currently
untested. In addition to auto-generating a REST proxy server, a
swagger.json is also generated which allows for gRPC-like native
objects with higher-level clients, and also for auto-generated
documentation.

Due to limitations with accepting raw byte strings as parameters, some
RPC’s have been modified to take both raw-bytes and string arguments.
Additionally a new RPC has been added ‘NewWitnessAddress’ since the
proxy doesn’t currently support enum-based arguments.

Currently the proxy server is embedded within the daemon as an active
HTTP server, however we may want to package the proxy server as a
separate binary in the future. Similarly, we may want to add additional
configuration information which controls the optional inclusion of the
REST proxy.

Atm, just like the current gRPC interface, the REST API is fully
unauthenticated. Before moving to an initial alpha release after making
the necessary changes to meet the spec drafted in Milan, authentication
of the RPC interfaces will be addressed.

glide.lock

@@ -1,13 +1,14 @@
-hash: 3047655dd4d303e49360573568bb046155e047519243c0ed8b1f8be2fcaf02de
-updated: 2016-09-20T16:28:15.627923101-07:00
+hash: db69bdd1de1bff79275a16649b87f5c5769a7ce6e889a9babf96dea470d931bf
+updated: 2016-10-15T14:19:38.70874686-07:00
 imports:
 - name: github.com/awalterschulze/gographviz
-  version: 761fd5fbb34e4c2c138c280395b65b48e4ff5a53
+  version: d4d8514752339899250316f88a7907468e8eca7e
   subpackages:
   - ast
   - parser
-  - scanner
   - token
+  - errors
+  - lexer
 - name: github.com/BitfuryLightning/tools
   version: b36ae00916b800503504455f7afeb3159bd5ee35
   subpackages:
@@ -55,11 +56,20 @@ imports:
   subpackages:
   - spew
 - name: github.com/golang/protobuf
-  version: 1f49d83d9aa00e6ce4fc8258c71cc7786aec968a
+  version: 98fa357170587e470c5f27d3c3ea0947b71eb455
   subpackages:
   - proto
+  - jsonpb
+  - protoc-gen-go/descriptor
+- name: github.com/grpc-ecosystem/grpc-gateway
+  version: a8f25bd1ab549f8b87afd48aa9181221e9d439bb
+  subpackages:
+  - runtime
+  - third_party/googleapis/google/api
+  - utilities
+  - runtime/internal
 - name: github.com/howeyc/gopass
-  version: 26c6e1184fd5255fa5f5289d0b789a4819c203a4
+  version: f5387c492211eb133053880d23dfae62aa14123d
 - name: github.com/lightningnetwork/lightning-onion
   version: 81647ffa2c5e17c0447d359e1963a54e18be85c4
 - name: github.com/roasbeef/btcd
@@ -84,7 +94,7 @@ imports:
   - txsort
   - base58
 - name: github.com/roasbeef/btcwallet
-  version: 1fd2d6224698e14591d06f2a10b24e86494cc19f
+  version: 7acd18a96697b180b631631108f1a15448de369f
   subpackages:
   - chain
   - waddrmgr
@@ -104,7 +114,7 @@ imports:
 - name: github.com/urfave/cli
   version: a14d7d367bc02b1f57d88de97926727f2d936387
 - name: golang.org/x/crypto
-  version: 6ab629be5e31660579425a738ba8870beb5b7404
+  version: 5f31782cfb2b6373211f8f9fbf31283fa234b570
   subpackages:
   - hkdf
   - nacl/secretbox
@@ -115,7 +125,7 @@ imports:
   - pbkdf2
   - ssh/terminal
 - name: golang.org/x/net
-  version: f4fe4abe3c785295ddf81c7f1823bcd3bad391b6
+  version: 8b4af36cd21a1f85a7484b49feb7c79363106d8e
   subpackages:
   - context
   - http2
@@ -125,17 +135,17 @@ imports:
   - lex/httplex
   - internal/timeseries
 - name: golang.org/x/sys
-  version: 8f0908ab3b2457e2e15403d3697c9ef5cb4b57a9
+  version: 9bb9f0998d48b31547d975974935ae9b48c7a03c
   subpackages:
   - unix
 - name: google.golang.org/grpc
-  version: 0032a855ba5c8a3c8e0d71c2deef354b70af1584
+  version: b1a2821ca5a4fd6b6e48ddfbb7d6d7584d839d21
   subpackages:
   - grpclog
   - codes
+  - metadata
   - credentials
   - internal
-  - metadata
   - naming
   - transport
   - peer