Show user who installed and activated the plugin

[maor]

2 different pieces of information:

• Who installed it
• Who last activated it

[swissspidy]

You have to keep in mind that this information can't be retrieved when

• someone uploads a plugin via FTP (can't be tracked)
• someone activates a plugin via WP-CLI

Otherwise it's probably fairly basic. Maybe I'll have time to hack something together.