Improve CLI Help content (#561)

Erica/Josh did a pass at all the CLI --help output to clean it up and
make it more readable.

Co-authored-by: Josh Berry <josh.berry@temporal.io>

Author: fairlydurable

Makefile

@@ -0,0 +1,11 @@
+.PHONY: all gen build
+
+all: gen build
+
+gen: temporalcli/commands.gen.go
+
+temporalcli/commands.gen.go: temporalcli/commandsmd/commands.md
+	go run ./temporalcli/internal/cmd/gen-commands
+
+build:
+	go build ./cmd/temporal