Show quick summary information in the intro/help screen

[adamsky]

Intro screen could show something like the following:

most recent downloads: 
<crate>  | <crate> | <crate> | <crate>

just updated:
<crate> | <crate> | <crate> | <crate>

new crates:
<crate> | <crate> | <crate> | <crate>

[adamsky]

implemented in 8dfb127