Clarify keep history setting

This is a frequently asked question - what is "keep message history"?

Merge branch 'feature/read-only-rooms' of https://github.com/garychapman/Rocket.Chat into garychapman-feature/read-only-rooms

# Conflicts:
#	packages/rocketchat-lib/server/methods/createChannel.coffee

Add more checks to methods

check if the user being removed is the last owner of the room

Add ability of multiple users invitation to slash command `invite`

Add load more button to permissions manager

Nokobon custom emoji

# Conflicts:
#	packages/rocketchat-custom-emoji/server/methods/deleteCustomEmoji.js
#	packages/rocketchat-emoji-custom/server/methods/uploadEmojiCustom.js

Merge branch 'check_If_Removed_User_Is_Owner' of github.com:RocketChat/Rocket.Chat into check_If_Removed_User_Is_Owner

# Conflicts:
#	packages/rocketchat-channel-settings/client/views/channelSettings.coffee
#	packages/rocketchat-channel-settings/client/views/channelSettings.html
#	packages/rocketchat-channel-settings/server/methods/saveRoomSettings.coffee
#	packages/rocketchat-lib/server/methods/addUserToRoom.coffee
#	packages/rocketchat-ui/views/app/room.coffee
#	server/methods/createChannel.coffee
#	server/methods/createPrivateGroup.coffee
#	server/methods/joinRoom.coffee
#	server/startup/roomPublishes.coffee

Add setting to disable LDAP fallback to default account system

Fix error with CustomOAuth on startup