Internally rename restorer.Filter -> restorer.SelectForRestore to make
semantic clear.
In addition, swap parameters to filepath.Match() so that the pattern can
really be matched.
Limitation: The filter only works on the filename, not on any path
component, e.g. '*.go' selects all go files, 'subdir/foo*' doesn't
select anything.
Fixes#202.
This just matches the passed pattern against the full source path with
filepath.Match which, in contrast go filepath.Glob, doesn't match the
directory separator with '*' and is not terribly useful that way.
Someone should replace that by a more sophisticated matcher.
