Pass a file into YamlAliasStore.

This allows it to be used to read other files, such as bundled
defaults.

Change-Id: I1db09ccf6e8048e00e8c73da4962f68c8bb8fb85
Reviewed-on: http://gerrit.dmdirc.com/3555
Reviewed-by: Greg Holmes <greg@dmdirc.com>
Automatic-Compile: DMDirc Build Manager