Cleanup zsh functions and add unbkp()

Add unbkp() that reverses bkp().
Use shorter zsh syntax for disowning a background job.
Add usage string to mangrep.
Expect clang-format config to be in XDG_CONFIG_HOME. Add functionality
of comments.
Use `command` where we want a command to be taken as external.

.config/zsh/plugins/functionsPre.zsh

@@ -4,18 +4,18 @@
 ## List items in trash if no argument is specified
 function _trash_list_default() {
 	if [ $# -eq 0 ]; then
-		trash-list
+		command trash-list
 	else
-		\trash "$@"
+		command trash "$@"
 	fi
 }
 
 ## Open nemo in current directory if no argument is specified
 function _nemo_wd_default() {
 	if [ $# -eq 0 ]; then
-		\nemo ./
+		command nemo ./
 	else
-		\nemo "$@"
+		command nemo "$@"
 	fi
 }