Change the `avocado plugins` output

[beraldoleal]

Avocado 2020 vision is:

"A leaner and more flexible Avocado with a reduced learning curve."

Currently, avocado plugins command displays some internal implementation details. To improve our user experience, we could print a better output, focused on Avocado users instead of Avocado developers.

A possible output could be:

$ avocado plugins

package                                       provides   description
------------------------------------------------------------------------
avocado-framework-plugins-foo    bar,test   blabalba
avocado-framework-plugins-foo    bar,test   blabalba
avocado-framework-plugins-foo    bar,test   blabalba
avocado-framework-plugins-foo    bar,test   blabalba
avocado-framework-plugins-foo    bar,test   blabalba
avocado-framework-plugins-foo    bar,test   blabalba
avocado-framework-plugins-foo    bar,test   blabalba

And to know more details about a specific plugin, we could have another command, like avocado plugin show foo.

[dkarpelevich]

Hi @beraldoleal , what would you like to see as provides in this table? The output can look like:

(venv) [user@host avocado]$ avocado plugins
Plugins that generate job result based on job/test events (result_events):
package    | provides      | description
=======================================================================
fetchasset | provides stub | Fetch assets before the test run
human      | provides stub | Human Interface UI
journal    | provides stub | Journal event based results implementation
resultsdb  | provides stub | Resultsdb result support
tap        | provides stub | TAP - Test Anything Protocol results