IPMI SEL commands

Corresponding Igor API PR: https://github.com/emaadmanzoor/igor-rest-api/pull/12

Adds commands:

   * `igor sel info`
   * `igor sel time [--time <string>]`
   * `igor sel list [--extended]`
   * `igor sel get <record id>`
   * `igor sell add <filename>`
   * `igor sel clear`