fix some warnings (unused imports), remove dead code

src/org/sflphone/adapters/AccountSelectionAdapter.java

src/org/sflphone/fragments/AccountCreationFragment.java

src/org/sflphone/fragments/CallFragment.java

src/org/sflphone/fragments/DetailsHistoryEntryFragment.java

src/org/sflphone/fragments/DialingFragment.java

src/org/sflphone/fragments/FileExplorerDFragment.java

src/org/sflphone/fragments/IMFragment.java

src/org/sflphone/fragments/MenuFragment.java

src/org/sflphone/fragments/NestedSettingsFragment.java

src/org/sflphone/fragments/SecurityAccountFragment.java

src/org/sflphone/loaders/HistoryLoader.java

src/org/sflphone/model/BubblesView.java

src/org/sflphone/service/SipService.java