Fix checkstyle order for static imports.

We put them below all other imports, checkstyle defaults to below
each group.

Also fix the formatting of the checkstyle config, replacing tabs
with spaces and fixing broken indentation/spacing.

Change-Id: I46f71e58f9ff4f8719ba59ff95d6415095058d21
Reviewed-on: http://gerrit.dmdirc.com/3121
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Greg Holmes <greg@dmdirc.com>