Moving cache variable to template instead of in the struct.

Similar to GitHub:
https://github.com/blog/2111-issue-and-pull-request-templates

Priority:
- root
- .gogs
- .github

This is fixup for ea375c0dcc. The bug was not
visible because commit.RefUrl was always returning empty url due regression
described in https://github.com/gogits/git-module/pull/4

This makes the code more strict since you can't assign or compare
values of different types without proper cast.

- Unified/Inline Diff-View Selectable

- User profile un/follow
- List user's followers/following

We only handle branch selection for repo home and commits pages, so the
redirection URL is based on PageIsCommits

I've mostly duplicated the dropdown code from repo/home.tmpl, which
basically only required a change to the URL. This could probably be
broken out into something more modular.

This commit improves templates readability, since all of them use consistent
indent with all template command blocks indented too.

1. Indents both HTML containers such as <div>, <p> and Go HTML template blocks
   such as {{if}} {{with}}

2. Cleans all trailing white-space

3. Adds trailing last line-break to each file

Most commit in Git are expected to follow standard of single header line,
followed by description paragraphs, separated by empty line from previous block.

Previously Gogs were treating everything as single header. Now we are trying to
render only first line as header, but following lines (description chunks) as a
verbatim.