Make flags additive and clean up docs

This means that you have to turn on features now instead of disabling
them like auth and https.

In addition:
- Allow multiple options for auth (only password for now).
- Combine the install docs since they had many commonalities and
- generally simplified them (hopefully not too much).
- Move all example configs into docs/examples.

doc/fail2ban.md

@@ -0,0 +1,35 @@
+# Protecting code-server from bruteforce attempts
+code-server outputs all failed login attempts, along with the IP address,
+provided password, user agent and timestamp by default.
+
+When using a reverse proxy such as Nginx or Apache, the remote address may
+appear to be `127.0.0.1` or a similar address so `X-Forwarded-For` should be
+used instead. Ensure that you are setting this value in your reverse proxy:
+
+Nginx:
+```
+location / {
+  ...
+  proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+  ...
+}
+```
+
+Apache:
+```
+<VirtualEnv>
+  ...
+  SetEnvIf X-Forwarded-For "^.*\..*\..*\..*" forwarded
+  ...
+</VirtualEnv>
+```
+
+It is extremely important that you ensure that your code-server instance is not
+accessible from the internet (use localhost or block it in your firewall).
+
+## Fail2Ban
+Fail2Ban allows for automatically banning and logging repeated failed
+authentication attempts for many applications through regex filters. A working
+filter for code-server can be found in `./code-server.fail2ban.conf`. Once this
+is installed and configured correctly, repeated failed login attempts should
+automatically be banned from connecting to your server.