modified /etc/default/drone to use DRONE_ prefix for env vars

debian/drone/etc/default/drone

@@ -10,39 +10,39 @@
 #DRONED_OPTS="--port=:80"
 
 # Email configuration
-#SMTP_HOST=
-#SMTP_PORT=
-#SMTP_FROM=
-#SMTP_USER=
-#SMTP_PASS= 
+#DRONE_SMTP_HOST=
+#DRONE_SMTP_PORT=
+#DRONE_SMTP_FROM=
+#DRONE_SMTP_USER=
+#DRONE_SMTP_PASS= 
 
 # GitHub configuration
-#GITHUB_CLIENT=
-#GITHUB_SECRET=
+#DRONE_GITHUB_CLIENT=
+#DRONE_GITHUB_SECRET=
 
 # GitHub Enterprise configuration
-#GITHUB_ENTERPRISE_CLIENT=
-#GITHUB_ENTERPRISE_SECRET=
-#GITHUB_ENTERPRISE_URL=
-#GITHUB_ENTERPRISE_API=
+#DRONE_GITHUB_ENTERPRISE_CLIENT=
+#DRONE_GITHUB_ENTERPRISE_SECRET=
+#DRONE_GITHUB_ENTERPRISE_URL=
+#DRONE_GITHUB_ENTERPRISE_API=
 
 # GitLab configuration
-#GITLAB_URL=
+#DRONE_GITLAB_URL=
 
 # Atlassian Bitbucket configuration
-#BITBUCKET_CLIENT=
-#BITBUCKET_SECRET=
+#DRONE_BITBUCKET_CLIENT=
+#DRONE_BITBUCKET_SECRET=
 
 # Atlassian Stash configuration
-#STASH_CLIENT=
-#STASH_SECRET=
-#STASH_URL=
-#STASH_API=
+#DRONE_STASH_CLIENT=
+#DRONE_STASH_SECRET=
+#DRONE_STASH_URL=
+#DRONE_STASH_API=
 
 # Optional global configuration options.
 #
 # This allows you, for example, to set a default Hipchat token
 # so that you don't need to specify in each .drone.yml file.
-#HIPCHAT_TOKEN=
-#SLACK_TOKEN=
-#ZAPIER_TOKEN=
+#DRONE_HIPCHAT_TOKEN=
+#DRONE_SLACK_TOKEN=
+#DRONE_ZAPIER_TOKEN=