ignore: ignore commands to other bots

Commands to other bots typically start with a special character,
like ! or @.
It is best that we look at the first character of each line and
ignore those.
Greet people as they come into the channel

For now, we only have one way to greet people but that is going
to change with translations.
alternatives: Add a alternatives framework

In the issues, this was called translations
alternatives: Make the bot use them. Fixes #7

For now used only on join grretings, but more to come

Also started the infra to include alternatives from modules