Move documentation under correct structure

Move the documentation into the resources folder, and update
the buck build configuration to include it.

Rename the command help file to have 'cmd-' prefix so that
it appears under the "Commands" heading on the documentation
index.

Change-Id: I211f01c2371be0dd4480af51ebcb91c69228bad6

BUCK

diff --git a/BUCK b/BUCK
index 4d48a44..f270ac2 100644
--- a/BUCK
+++ b/BUCK
@@ -1,6 +1,7 @@
 gerrit_plugin(
   name = 'helloworld',
   srcs = glob(['src/main/java/**/*.java']),
+  resources = glob(['src/main/resources/**/*']),
   manifest_entries = [
     'Gerrit-SshModule: com.google.gerrit.plugins.HelloWorldCommandModule'
   ]

src/main/resources/Documentation/cmd-print.md

diff --git a/Documentation/ssh-commands/print.md b/src/main/resources/Documentation/cmd-print.md
similarity index 100%
rename from Documentation/ssh-commands/print.md
rename to src/main/resources/Documentation/cmd-print.md