monitor: add cli11 argument parsing

Replace our custom argument parser with one from CLIUtils.

This results in a number of minor behavioral differences.
 - The -? option is no longer recognized as an alias for -h/--help.
 - The original parser returned EXIT_FAILURE in all cases, but CLIUtils
   uses different non-zero error codes in different situations.
 - Minor changes to help text descriptions:
----new----
Usage: build/phosphor-unit-failure-monitor.new [OPTIONS]

Options:
  -h,--help                   Print this help message and exit
  -s,--source TEXT REQUIRED
  -t,--target TEXT REQUIRED
  -a,--action ENUM:value in {start->0,stop->1} OR {0,1} REQUIRED

----old----
Usage: build/phosphor-unit-failure-monitor [options]
Options:
    --help             Print this menu
    --source=<source>  The source unit to monitor
    --target=<target>  The target unit to start or stop
    --action=<action>  Target unit action - start or stop

 - The original parser displays the full help text on error, CLIUtils
   does not:

----new----
$ phosphor-unit-failure-monitor
--source is required
Run with --help for more information.

----old----
$ phosphor-unit-failure-monitor
ERROR: Source not specified
Usage: build/phosphor-unit-failure-monitor [options]
Options:
    --help             Print this menu
    --source=<source>  The source unit to monitor
    --target=<target>  The target unit to start or stop
    --action=<action>  Target unit action - start or stop

Change-Id: I2417d9c857c6d8fc04807fe4729d2fa154e746a3
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/subprojects/CLI11.wrap b/subprojects/CLI11.wrap
new file mode 100644
index 0000000..2e5a95b
--- /dev/null
+++ b/subprojects/CLI11.wrap
@@ -0,0 +1,6 @@
+[wrap-git]
+url = https://github.com/CLIUtils/CLI11.git
+revision = HEAD
+
+[provide]
+CLI11 = CLI11_dep