Bug 952307 - Move some addon-private JSM's to a subdirectory. r=Unfocused

--HG--
rename : toolkit/mozapps/extensions/AddonLogging.jsm => toolkit/mozapps/extensions/internal/AddonLogging.jsm
rename : toolkit/mozapps/extensions/AddonRepository.jsm => toolkit/mozapps/extensions/internal/AddonRepository.jsm
rename : toolkit/mozapps/extensions/AddonRepository_SQLiteMigrator.jsm => toolkit/mozapps/extensions/internal/AddonRepository_SQLiteMigrator.jsm
rename : toolkit/mozapps/extensions/AddonUpdateChecker.jsm => toolkit/mozapps/extensions/internal/AddonUpdateChecker.jsm
rename : toolkit/mozapps/extensions/LightweightThemeImageOptimizer.jsm => toolkit/mozapps/extensions/internal/LightweightThemeImageOptimizer.jsm
rename : toolkit/mozapps/extensions/PluginProvider.jsm => toolkit/mozapps/extensions/internal/PluginProvider.jsm
rename : toolkit/mozapps/extensions/SpellCheckDictionaryBootstrap.js => toolkit/mozapps/extensions/internal/SpellCheckDictionaryBootstrap.js
rename : toolkit/mozapps/extensions/XPIProvider.jsm => toolkit/mozapps/extensions/internal/XPIProvider.jsm
rename : toolkit/mozapps/extensions/XPIProviderUtils.js => toolkit/mozapps/extensions/internal/XPIProviderUtils.js