add bing langauge code
Merge branch 'master' into multilang-v2
add entry language data
add IsCurrent flag for LanguageEntry
modify GetEntry API
Merge branch 'master' into multilang-v2
add billing
add FreeTrialLeftDays
Merge branch 'master' into multilang-v2

Conflicts:
	data.go
Merge branch 'master' into multilang-v2
add get Knowledgebase overview api
add update knowledge overview
Merge branch 'master' into multilang-v2
add language code for wiki section
add switch wiki section version api
Merge branch 'master' into multilang-v2
add GetPaymentSession
add SyncBilling
add Localed Map
add api for machine translations for wiki section