More visual information in PR/Issue/Branch view.

[kounoike]

This PR makes more visual information to improve understandability.

• show branch name with color (same algorithm to TextAvatar)
  • in Branches view
  • in PR view
• show avatar on top of issue/PR
• show Issue/PR icon
• skip owner name in PR description. (n commits into root:master from root:pr => n commits into master from pr)

branch colors:

Before submitting a pull-request to GitBucket I have first:

• read the contribution guidelines
• rebased my branch over master
• verified that project is compiling
• verified that tests are passing
• squashed my commits as appropriate (keep several commits if it is relevant to understand the PR)
• marked as closed using commit message all issue ID that this PR should correct

[zexxar]

This would be a good function to make it easier to understand the branching. Please add.