New I2PFragmentBase so Fragments can access RouterContext, migration changes

src/net/i2p/android/router/activity/I2PActivityBase.java

src/net/i2p/android/router/activity/MainActivity.java

src/net/i2p/android/router/fragment/I2PFragmentBase.java

src/net/i2p/android/router/fragment/MainFragment.java

src/net/i2p/android/router/fragment/NewsFragment.java

src/net/i2p/android/router/fragment/PeersFragment.java

src/net/i2p/android/router/fragment/VersionDialog.java

src/net/i2p/android/router/fragment/WebFragment.java