Rewrite resize() method to depend on _resizable.
Rewrite resize() method to depend on _resizable.

All class for which _resizable is True should define a resize method.

Prompted by a lot of pylint 'abstract-method' warnings.

Signed-off-by: mulhern <7b51bcf507bcd7afb72bf8663752c0ddbeb517f6@redhat.com>

vojtechtrefny/blivet,rhinstaller/blivet,rhinstaller/blivet,AdamWill/blivet,AdamWill/blivet,jkonecny12/blivet,jkonecny12/blivet,vpodzime/blivet,dwlehman/blivet,rvykydal/blivet,dwlehman/blivet,vojtechtrefny/blivet,rvykydal/blivet,vpodzime/blivet