[2.1-backport] Fix trailing slash used in url rewrites

[ihor-sviziev]

My pull request #10043 has been merged to develop branch. This PR adds the same changes to 2.1-develop branch

Description

Admin user configured two URL rewrites in Admin UI. Frontend user may request the page with or without trailing slash. In some case Magento will return 404 page.
We would like to avoid content duplication for the requests with and without trailing slash. If request path has configured url_rewrite (w/ or w/o trailing slash) redirect to this page automatically. If requested path matches configuration, just follow redirect rules.

Fixed Issues (if relevant)

1. Product URL Suffix "/" results in 404 error #4876 Product URL Suffix "/" results in 404 error
2. Slash as category URL suffix gives 404 error on all category pages #3872 Slash as category URL suffix gives 404 error on all category pages
3. Multiple URLs causes duplicated content #4660 Multiple URLs causes duplicated content
4. Custom URL Rewrite where the request path ends with a forward slash is not matched #8264 Custom URL Rewrite where the request path ends with a forward slash is not matched

Related pull requests

1. Fix trailing slash used a product URL suffix #7041 Fix trailing slash used a product URL suffix
2. Fixes problem with url rewrites not being matched when the request path has a trailing forward slash #8319 Fixes problem with url rewrites not being matched when the request path has a trailing forward slash

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)