inviteText and joinText

[H7-25]

The sending of inviteText and joinText logic it's wrong, it's based just on the condition isQuery so every time inviteText is sent for private conferences , and every time inviteText is sent for channel conferences. This get the users confused.
Probably the more simple solution for private conference is just send the invite to the conference message and avoid to sent the join one (jitsi itself notify if someone join the conference).
About conference for channels should be fine just notify in the channel the conference is active (exist) or not.