tweak color env variable options

As noted in mylog's 2b1085c:
Looks like both the GNU tools' --color argument and cargo's
CARGO_TERM_COLOR expect always/never rather than on/off. Match that.
Might as well understand off/no/false and on/yes/true also.

.github/workflows/ci.yml

@@ -3,6 +3,7 @@ on: [push, pull_request]
 
 env:
   CARGO_TERM_COLOR: always
+  MOONFIRE_COLOR: always
   RUST_BACKTRACE: 1
 
 jobs:

guide/troubleshooting.md

@@ -46,8 +46,8 @@ Logging options are controlled by environment variables:
     [glog](https://github.com/google/glog) package) and `google-systemd` (a
     variation for better systemd compatibility).
 *   `MOONFIRE_COLOR` controls color coding when using the `google` format.
-    It accepts `on`, `off`, or `auto`. `auto` means to color code if stderr
-    is a terminal.
+    It accepts `always`, `never`, or `auto`. `auto` means to color code if
+    stderr is a terminal.
 *   Errors include a backtrace if `RUST_BACKTRACE=1` is set.
 
 If you use Docker, set these via Docker's `--env` argument.
@@ -59,8 +59,8 @@ format:
 I20210308 21:31:24.255 main moonfire_nvr] Success.
 LYYYYmmdd HH:MM:SS.FFF TTTT PPPPPPPPPPPP] ...
 L    = level:
-       E = error
-       W = warn
+       E = error; when color mode is on, the message will be bright red.
+       W = warn;  "    "     "    "  "   "   "       "    "  "      yellow.
        I = info
        D = debug
        T = trace
@@ -72,7 +72,7 @@ MM   = minute
 SS   = second
 FFF  = fractional portion of the second
 TTTT = thread name (if set) or tid (otherwise)
-PPPP = module path
+PPPP = log target (usually a module path)
 ...  = message body
 ```
 

server/Cargo.lock

@@ -1274,7 +1274,7 @@ dependencies = [
 [[package]]
 name = "mylog"
 version = "0.1.0"
-source = "git+https://github.com/scottlamb/mylog#1406a8d794d799971e0e1079d5188d2dc339c584"
+source = "git+https://github.com/scottlamb/mylog#2b1085cfb3bd0b1f2afe7d8085045d81858c0050"
 dependencies = [
  "chrono",
  "libc",