new testnet window .ico file

Signed-off-by: Jonas Schnelli <jonas.schnelli@include7.ch>
embed bitcoin_testnet.ico in bitcoin-qt.exe (usable for shortcuts)
Merge pull request #2519 from jonasschnelli/new_testnet_ico_file

new testnet ico file
Add comments to UNIX Makefile regarding USE_UPNP

The tri-state nature of USE_UPNP isn't immediately obvious, so paste
the explanation from doc/build-unix.txt as a comment in the makefile.
new splash screen

why:

- the current splash-screen has no referring to official images on - https://en.bitcoin.it/wiki/Promotional_graphics
- the current splash screen only exists in a low res jpg
- current splash screen looks dark and "hackish"
- new splash screen should generate positive, "trust-emotions".
- new splash screen gives the user infos about the running client.
- new splash screen can handle long messages (in a lot of - languages the text is cropped in current release)

- new size (x2) 400x312

- contains textual information about the client
- textinfos are dynamicly written to the pixmap

when -testnet is switch on, the splashscreen will show the bitcoin logo in testnet-color (as well as a text [testnet])

example: https://dl.dropbox.com/u/7383846/new_bitcoin_splash.png
new toolbar icon for liunx/win fix #2518

On black toolbars, the new icon doesn't look very well.
Now the toolbar icon has again a transparent "B" for better style on toolbars.
Does not affect the mac client.

Signed-off-by: Jonas Schnelli <jonas.schnelli@include7.ch>
Merge pull request #2537 from jonasschnelli/toolbaricon_linux

new toolbar icon for liunx/win fix #2518
Merge pull request #2536 from jcalvinowens/makefile-clarifying-comments

Add comments to UNIX Makefile regarding USE_UPNP
Merge pull request #2524 from jonasschnelli/new_splashscreen_fresh

new splash screen