command-line-interface: "application process" -> "container process"

"Application process" was an early contender for this concept [1,2],
but there was pushback on that [3] and now "container process" is the
preferred term.

The initial "container process" phrasing landed in 15dee2e (runtime:
Add prestart/poststop hooks, 2015-08-03) around the same time as the
initial glossary work.

[1]: #107 (comment)
[2]: #107 (comment)
[3]: #107 (comment)

Signed-off-by: W. Trevor King <wking@tremily.us>

command-line-interface.md

@@ -53,11 +53,11 @@ $ echo $?
   * *`--id <ID>`* Set the container ID when creating a container.
     If not set, the runtime is free to pick any ID that is not already in use.
   * *`--bundle <PATH>`* Override the path to the [bundle directory][bundle] (defaults to the current working directory).
-* *Standard streams:* The runtime MUST attach its standard streams directly to the application process without inspection.
+* *Standard streams:* The runtime MUST attach its standard streams directly to the container process without inspection.
 * *Environment variables*
   * *`LISTEN_FDS`:* The number of file descriptors passed.
-    For example, `LISTEN_FDS=2` would mean that the runtime MUST pass file descriptors 3 and 4 to the application process (in addition to the standard streams) to support [socket activation][systemd-listen-fds].
-* *Exit code:* The runtime MUST exit with the application process's exit code.
+    For example, `LISTEN_FDS=2` would mean that the runtime MUST pass file descriptors 3 and 4 to the container process (in addition to the standard streams) to support [socket activation][systemd-listen-fds].
+* *Exit code:* The runtime MUST exit with the container process's exit code.
 
 #### Example