Rename and delete files and directories in the Web IDE

I should be able to rename and delete files in the Web IDE so that I don't have to leave the Web IDE to the repository file list to do this.

Proposal

• add delete button to file/directory drop down in file tree
• add rename button to file/directory drop down in file tree

Design

• Get rid of the plus icon, and replace it with a menu icon
• For files, there can already exist icons in the right side of the list element. These should be shoved aside with a small animation similar to:

• Files menu should consist of:
  • Rename
  • Duplicate https://gitlab.com/gitlab-org/gitlab-ce/issues/49398
  • Move https://gitlab.com/gitlab-org/gitlab-ce/issues/49397
  • Delete
• Directory menu should consist of:
  • New file
  • Upload file
  • New folder
  • SEPARATOR hr
  • Rename
  • Duplicate https://gitlab.com/gitlab-org/gitlab-ce/issues/49398
  • Move https://gitlab.com/gitlab-org/gitlab-ce/issues/49397
  • Delete
• The menu will display dedicated icons for each item
• The header has always visible options, these are not extended here/much, so we can display them directly with dedicated icons.

This results in:

• from top to down -> default, hover, active/focus

Icons

You can find them in gitlab-svgs.

• New file --> doc-new
• Upload file --> upload
• New folder --> folder-new
• Rename --> pencil
• Duplicate --> dupilcate
• Move --> arrow-right
• Delete --> remove