Moved I2PProperties callback to the RouterContext.

apps/desktopgui/src/net/i2p/desktopgui/Main.java

...sktopgui/src/net/i2p/desktopgui/router/RouterManager.java

...terconsole/java/src/net/i2p/router/web/ContentHelper.java

core/java/src/net/i2p/I2PAppContext.java

core/java/src/net/i2p/util/I2PProperties.java

router/java/src/net/i2p/router/RouterContext.java