Auto-generate markdown command docs (#4451)

* Finish updating

* a couple improvements

* Update renames

* cleanup examples

docs/commands/path_parse.md

@@ -0,0 +1,39 @@
+---
+title: path parse
+layout: command
+version: 0.59.0
+---
+
+Convert a path into structured data.
+
+## Signature
+
+```> path parse --columns --extension```
+
+## Parameters
+
+ -  `--columns {table}`: Optionally operate by column path
+ -  `--extension {string}`: Manually supply the extension (without the dot)
+
+## Examples
+
+Parse a path
+```shell
+> '/home/viking/spam.txt' | path parse
+```
+
+Replace a complex extension
+```shell
+> '/home/viking/spam.tar.gz' | path parse -e tar.gz | update extension { 'txt' }
+```
+
+Ignore the extension
+```shell
+> '/etc/conf.d' | path parse -e ''
+```
+
+Parse all paths under the 'name' column
+```shell
+> ls | path parse -c [ name ]
+```
+