overhaul of the testnet icon (green color) and the toolbar icons

- redefined the green color
- created new toolbar icons
- updated the assets-attribution.txt

Signed-off-by: Jonas Schnelli <jonas.schnelli@include7.ch>

doc/assets-attribution.txt

@@ -38,11 +38,6 @@ Designer: http://www.everaldo.com
 Icon Pack: Crystal SVG
 License: LGPL
 
-Icon: src/qt/res/icons/toolbar.png
-Designer: Bitboy (optimized for 16x16 by Wladimir van der Laan)
-License: Public Domain
-Site: https://bitcointalk.org/?topic=1756.0
-
 Icon:  scripts/img/reload.xcf (modified),src/qt/res/movies/update_spinner.mng
 Icon Pack: Kids
 Designer: Everaldo (Everaldo Coelho)
@@ -61,6 +56,7 @@ License: Oxygen icon theme is dual licensed. You may copy it under the Creative
 
 Icon: src/qt/res/icons/bitcoin.icns, src/qt/res/src/bitcoin.svg,
       src/qt/res/src/bitcoin.ico, src/qt/res/src/bitcoin.png,
-      src/qt/res/src/bitcoin_testnet.png, docs/bitcoin_logo_doxygen.png
+      src/qt/res/src/bitcoin_testnet.png, docs/bitcoin_logo_doxygen.png,
+      src/qt/res/icons/toolbar.png, src/qt/res/icons/toolbar_testnet.png
 Designer: Jonas Schnelli (based on the original bitcoin logo from Bitboy)
 License: MIT