Remove unused title parameter.

It is always overridden by to humanized source branch name by
MergeRequests::BuilService, which is used by new_project_merge_request_path.
Implement cross-project Markdown references

Enable linking to commits, merge requests, and issues in other projects
by prepending a namespaced project path to the reference.
Fix ReferenceExtractor

The cross-project reference feature broke the ReferenceExtractor class;
this fixes it.
Track projects in ReferenceExtractor

Store both the project and identifier of extracted references.  This
prevents `ReferenceExtractor` from returning objects in the wrong
project for cross-project references.
Make Mentionables work for cross-project refs

Add a note to merge requests and issues when they're mentioned by a
merge request, issue, or commit in another project.
Fix fa-download icon
Fix external issue links

Display the project path in links to issues in other projects that use
an external issue tracker.
Fix external commit links

Display the '@' character for links to commits in other projects.
Fix cross-project reference test

Test for the correct link text in cross-project references.
Merge pull request #7960 from Soullivaneuh/fa-fix

Fix fa-download icon
Make Spinach test names consistent

- do not add Feature to feature titles
- titleize feature titles
- put steps on the same path as .feature files
- make feature titles match their path
Merge pull request #7933 from mr-vinn/cross-project-markdown

Implement cross-project Markdown references
Merge pull request #7940 from cirosantilli/uniform-spinach-names

Make Spinach test names consistent [failure unrelated]
Merge pull request #7379 from cirosantilli/remove-title

[minor-refactor] Remove unused title parameter on merge request creation helper.