Render commit msg as header + verbatim description

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.

Fix misspelled words

UI: Use more subtle grey SHA1 labels

With grey SHA1 labels, we should consider having also more subtle strips on
commits list. As current strips blend too much with grey SHA1 labels and top
bar, making hard to distinguish headers from content.

UI: Remove CSS rule making last-commit SHA bold

Current green SHA1 labels are more pronounced than other UI elements attracting
attention as if they were most important thing in the UI, while they are not as
important, especially without real Git client.

Using grey SHA1 labels makes the UI more balanced, less aggressive and lets
user to focus on other content elements.

NOTE: Neither GitHub or Bitbucket uses so heavy pronunciation as Gogs.

This removes remains from old design, that was not cleaned by previous #2068 PR.

Further layout fixes

Otherwise the fix will be overwritten by next _octicons.less update.

This is follow-up for 22b0dfbb35.

Merges repo/sidebar.tmpl with repo/header.tmpl and makes every repo page use
middleware.RepoRef() necessary to display information on this menu.

Repo file list layout & misc fixes

This uses a CSS trick making first th to be relative block with width equal to
first two columns, effectively working around inability to use colspan="2" on
first row that was breaking "fixed-layout" for tables.

Also use grey header for last-commit SHA1 tag.

Translation: Add missing entry for new "code" tab