rename cmd_install_ functions

[snystrom]

These utilities can be used to check for things other than "installs" like API keys, etc. The function names should reflect this.

cmd_install_is_valid -> cmd_path_is_valid cmd_install_check -> cmd_path_check (change message from "install" -> "path")

ToDo

• [ ] Alias cmd_install family to cmd_path family
• [ ] deprecate cmd_install family