[various modules] Utilize Trigger.is_privmsg

Replace trigger.sender.startswith('#') checks with trigger.is_privmsg
in the following modules: admin, find, meetbot, reload, seen.
[tell] Fixes #418. Error when not enough args given
Say 'I am sending you a private message of all my commands' only if there is not a priv msg yet
Allow you specify language to search on wikipedia

using just one regex to parse laguage args. Thanks to @alexandernst

Allow you to set default language channel by channel

Fix two error, non-custom lang and error from wikipedia api.