Change convention for ignoring attribute routing prefixes to '~/'

Revert "Issue 1150: Add support for ignoring route prefixes to MVC attribute routing"

This reverts commit 5aedf25113a8c28af9e43ba9cd1247fd25ecabda.

Revert "Issue 1150: Add support to attribute routing for ignoring the route prefix"

This reverts commit 962c265473d77ec62dab3361886ca96178a8b886.