Lazy setup java plugin for Firefox on Debian amd64

In order to get it working we need to:

1. Install Iceweasel from our debian repository: sudo apt-get install iceweasel
2. Download the last java 64 bits from http://www.java.com/
3. Install Java accordingly to the instructions provided by the vendor (normally /usr/local/<your_java_directory> and create a sym link to java folder)
4. Since we are using the new java plugin (libnpjp2.so), we need to create a symb link into the plugins folder: ln -s /usr/local/<your_java_directory>/lib/amd64/libnpjp2.so /usr/lib/mozilla/plugins/ don't try to copy the plugin or you will get an error like "InitializeJVM: Assertion `foundJVM' failed"
5. Start iceweasel and test the plugin

I managed to get some problems with Java regarding to network configuration - it was trying to use IPV6. Since I don't use Java at all, I disabled the ipv6 from my system editing the file /etc/sysctl.conf adding the line net.ipv6.conf.all.disable_ipv6=1, after that executing sysctl -p made the change effective (alternatively, you can modify Java parameters to disable IPV6 only on it).