fixing default icon reference

So, this includes the following:

Updates on both /config.xml and /www/config.xml Files. After reading a lot, i realized the config file on the root, is the one used by cordova, and the one in www, is used by phonegap build app. After updating the root config file with the right icons and splash screens, we don't need any more a hook to copy the assets, this was a changed cordova introduced in the latest versions. The config file on www, still need all the same info from the other one, some things with different sintaxis, like <gap:splash> tags instead of <splash>, etc, but phonegap build app requires this.

Removed 'hooks/after_prepare/icons_and_splash.js' since is not needed anymore.

Fixed all icons and splash screens requirements and configuration.