Support "excludePaths" options in bitbucket-pipelines.yml's `condition` section

Bitbucket Pipelines currently support `includePaths` options in the `condition section:

          condition:
              changesets:
                 includePaths:
                   # only xml files directly under path1 directory
                   - "path1/*.xml"
                   # any changes in deeply nested directories under path2
                   - "path2/**"

It will be best that Pipelines supports `excludePaths` option for users who maintained a repository with a large number of directories in it.

• Having the `excludePaths` will increase the yml readability
• Easy for users to setup yml config when the repo has a large number of directories to track