docs(plugins): fix a broken link
fix(config): not append empty module if no custom launcher/rep/prep

Just to get rid off the confusing debug message:
"DEBUG [plugin]: Loading inlined plugin (defining )."
feat(config): log if no config file is specified

Now that Karma tries to be a bit more clever and tries `karma.conf.js` or `karma.conf.coffee`, it's helpful to know that no config file was loaded.
fix(watcher): allow parentheses in a pattern

Closes #728