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

Just use secondary menu instead custom ".head.meta", which simplifies code.

Also do not display repo URL action when we are in subdirectory or viewing a
file.

We have new tab, but we had no entry. That's why it was showing "code"
(lowercase) as this is text id, where we were expecting properly title cased
"Code" to be shown in English version.

Also add Polish translation "code=Kod".

This is more inline with way GitHub looks like and feels much more natural and
in style with rest of the interface.

Instead using own ellipsis, uses Semantic UI fixed single line table which
effectively applies ellipsis to all overflowing table cells.

NOTE: File list cannot use colspan="2" for 1st "Last commit" elements,
otherwise layout breaks with fixed table.

This is because SHA1 label is used in many other places, not only inside
.repository container.

Semantic UI .icon 1em font-size has priority over .octicon 16px, resulting
octicons rendered at 14px font-size, which is not okay since Octicons are meant
to be shown sizes that are multiples of 16px.

Update English translations

Just some phrasing changes to make the English translations sound more natural.

LDAP: Optional user name attribute specification

Consider following LDAP search query example:

    (&(objectClass=Person)(|(uid=%s)(mail=%s)))

Right now on first login attempt Gogs will use the text supplied on login form
as the newly created user name. In example query above the text matches against
both e-mail or user name. So if user puts the e-mail then the new Gogs user
name will be e-mail which may be undesired.

Using optional user name attribute setting we can explicitly say we want Gogs
user name to be certain LDAP attribute eg. `uid`, so even user will use e-mail
to login 1st time, the new account will receive correct user name.

Makefile improvements

add new mirror button to dashboard

We no longer need to manually build CSS files as Makefile keeps track of it.

This is pure cleanup commit.

This will ensure that running `make` we will get all necessary files built and
we do not need manually remember to rebuild them.

This speeds up single build/rebuild rather than install & build which compiles
everything twice, we just copy installed binary back to the project root.

This adds the button to create a new mirror on the dashboard at the same
place where "new repository" and "new organization" already exist.

Dockerfile for RaspberryPi is added.

Admin should be able to see all organizations

various fixes in gogs dump command

This is follow-up for 56c66ee486 allowing admin
to see private repositories, even when not being member of them.

Now, the dump cmd uses setting.CustomPath and setting.LogRootPath
instead of setting.WorkDir which was kind of broken if the gogs
binary was in a different directory than gogs data.
Additionally, the backup of setting.CustomPath directory is only done
if it exists.