Compiler warning fixes.

This fixes all warnings that I got while compiling with g++ 4.7.2:

 In file included from interface/src/Application.h:53:0,
                  from interface/src/Menu.cpp:36:
 interface/src/Menu.h: In constructor ‘Menu::Menu()’:
 interface/src/Menu.h:292:13: warning: ‘Menu::_scriptsLocation’ will be initialized after [-Wreorder]
 interface/src/Menu.h:289:27: warning:   ‘QPointer<LoginDialog> Menu::_loginDialog’ [-Wreorder]
 interface/src/Menu.cpp:82:1: warning:   when initialized here [-Wreorder]

 libraries/audio/src/AudioRingBuffer.cpp: In member function ‘qint64 AudioRingBuffer::writeData(const char*, qint64)’:
 libraries/audio/src/AudioRingBuffer.cpp:126:75: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]

 libraries/audio/src/PositionalAudioRingBuffer.cpp: In member function ‘bool PositionalAudioRingBuffer::shouldBeAddedToMix()’:
 libraries/audio/src/PositionalAudioRingBuffer.cpp:212:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]

 interface/ui/preferencesDialog.ui: Warning: The name 'horizontalLayout_11' (QHBoxLayout) is already in use, defaulting to 'horizontalLayout_111'.
 interface/ui/preferencesDialog.ui: Warning: The name 'horizontalSpacer_11' (QSpacerItem) is already in use, defaulting to 'horizontalSpacer_111'.

 interface/src/avatar/Avatar.cpp: In member function ‘void Avatar::initializeHair()’:
 interface/src/avatar/Avatar.cpp:587:21: warning: name lookup of ‘link’ changed [enabled by default]
 interface/src/avatar/Avatar.cpp:574:18: warning:   matches this ‘link’ under ISO standard rules [enabled by default]
 interface/src/avatar/Avatar.cpp:577:22: warning:   matches this ‘link’ under old rules [enabled by default]

 interface/src/ui/ApplicationOverlay.cpp: In member function ‘void ApplicationOverlay::renderControllerPointers()’:
 interface/src/ui/ApplicationOverlay.cpp:379:59: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]

 In file included from interface/src/ui/RunningScriptsWidget.cpp:14:0:
 interface/src/ui/RunningScriptsWidget.h: In constructor ‘RunningScriptsWidget::RunningScriptsWidget(QWidget*)’:
 interface/src/ui/RunningScriptsWidget.h:61:18: warning: ‘RunningScriptsWidget::_scriptsModel’ will be initialized after [-Wreorder]
 interface/src/ui/RunningScriptsWidget.h:60:27: warning:   ‘QSortFilterProxyModel RunningScriptsWidget::_proxyModel’ [-Wreorder]
 interface/src/ui/RunningScriptsWidget.cpp:27:1: warning:   when initialized here [-Wreorder]