implement config presets (closes #20)
    
      * added PresetSeed class for creating default static presets via PresetSeed::NewPreset()
      * Config GUI reloads each time brought to front
      * consolidated Config::populateComboboxes() into Config::loadConfig()
      * consolidated Gstreamer::Configure* methods into Gstreamer::ConfigureTodo()
      * removed model handles fropm Config and Controls GUI classes in favor of controller getters/setters
      * added AvCaster::GetConfigStore(), AvCaster::GetPresetIdx(), AvCaster::GetIsConfigPending(),
              AvCaster::GetPresetName(), AvCaster::GetPresetsNames(), AvCaster::GetCameraNames(),
              AvCaster::GetAudioNames(), AvCaster::GetCameraConfig(), AvCaster::GetCameraResolutions(),
              AvCaster::GetCameraResolution(), AvCaster::GetCameraPath(), AvCaster::GetCameraRate()
      * added AvCaster::StorePreset(), AvCaster::RenamePreset(),  AvCaster::DeletePreset(),
              AvCasterStore::storePreset(), AvCasterStore::renamePreset(), AvCasterStore::deletePreset()
      * added AvCasterStore::loadPreset(), AvCasterStore::presetsNames(), AvCasterStore::cameraNames(),
              AvCasterStore::audioNames(), AvCasterStore::getCameraConfig(), AvCasterStore::getCameraResolutions()
      * added Controls::rejectPresetChange(), Controls::setCreatePresetMode(), Controls::isCreatePresetMode()
      * added Config::configureSlider(), Config::configureTextEditor(), Config::configureCombobox(), Config::enableComponents()
      * added Controls::configureCombobox(), Controls::handleSaveButton(), Controls::handleNewButton(),
              Controls::handleDeleteButton(), Controls::handlePresetCombo(), Controls::toggleControls(),
              Controls::loadConfig(), Controls::rejectPresetChange()
      * added AvCaster::IsEnvironmentSane(), AvCaster::IsMutablePreset()
      * renamed AvCaster::ToggleConfig() to AvCaster::RefreshGui()