Add all Pytroll logo variants

[adybbroe]

Adding the remaining Pytroll logos, so that all logos available on the pytroll.org homepage is also available in pydecorate.

I think we have said we should avoid having large data files and png's in the repos, but these are not really big, and thought it would be natural for completeness to have all the current Pytroll logos available here. Before it was only one of the five.

We could also, in addition have the satpy logo in png and/or the svg with all of them. But doing the latter users would have to make png's themselves from the SVG. But maybe you think this is better?
Opinions @mraspaud @pnuu and @djhoese ? Or anyone else?

[coveralls]

Pull Request Test Coverage Report for Build 35

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 44.965%

---

Totals
Change from base Build 41:	0.0%
Covered Lines:	192
Relevant Lines:	427

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 35

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 44.965%

---

Totals
Change from base Build 41:	0.0%
Covered Lines:	192
Relevant Lines:	427

---

💛 - Coveralls

[codecov]

Codecov Report

Merging #15 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #15   +/-   ##
=======================================
  Coverage   44.83%   44.83%           
=======================================
  Files           4        4           
  Lines         426      426           
=======================================
  Hits          191      191           
  Misses        235      235           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update efa0f1f...9b02290. Read the comment docs.