[UX] better addons installation flow the first time

[Ivshti]

ideas:

• [ ] rather than saying "no content available" say "Please install more add-ons"
• [ ] first time you go to the addon catalog, show some explanation what it does
• [x] "more addons" button more noticable
• [x] when you go to the addon page from a type "movie", go to add-ons for movie, etc.

[alesinka]

Here are some ideas on this:

1. Addons page for the first time:

2. No streams found with a cat:

3. No streams without a cat:

[Ivshti]

This is good (sidenote: looks beautiful w/o rounded edges) - but the explainer on the catalog could use an icon or two..perhaps?

[alesinka]