webcommands: move help import into help command handler A subsequent patch will introduce an import cycle between mercurial.help and mercurial.hgweb.webcommands. Break the cycle by moving the import of mercurial.help into the web command that actually needs it.

webcommands: define a dict of available commands This will be used to hook web commands up to the help system. It also makes web commands work similarly as CLI commands.

webcommands: define web commands using a decorator Other parts of Mercurial have evolved to use decorators to declare commands or handlers. This patch gives the same treatment to web commands.