limits tags just on commit, show tags on commits page. close #1968

[kounoike]

This PR is answer for #1968. It limits tags on commit.

And this PR also provide tag list on commit history page.

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

[takezoe]

@kounoike I agree with showing tags on the commits list, but don't agree with limiting tags in the commit page quickly. I can merge first one immediately if you split this pull request into two pull requests.

[kounoike]

@takezoe How about changes like this (edit by dev-mode) screenshot? (tags are already expanded by click)

I think these changes are important

• add which tag on this commit or "tag xxx pointed to after n commits"
• add description for answer to "what tags are listed?"
• sort tags by tagged date or other criteria not alphabetical order

But it requires more discussion. So I will make new PR which contains only commits list page changes.