Fixes relative urls coming from api/v1

See https://github.com/drone/drone/issues/1701

RepoLink -> Link, RepoRelLink -> RelLink, FullRepoLink -> FullLink

Executed go fmt

getEngine() not handles DB parameters (#2972) (#2974)

Uses .AllCols() for Update in updateMirror()

Spanish traslation removed

Fixed a wrong way to ommit the --prune option in process.ExecDir() for MirrorUpdate function

Re: issues gogits/gogs#2863 and gogits/gogs#3231

As a result of modifications to the contents of the conf folder, `make bindata`
was run, causing an update to bindata.go.

Meta
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This commit will be rebased onto the 'develop' branch.

This prevents user retrieve arbitrary webhook by changing URL to
access webhook from other unauthorized repositories.

Since . and .. has browser automatical behaviors, we need to disallow those names.

Initially proposed by #2376 and fixes #3068 as well.

- Arbitrary file creation leading to command execution
- .md file creation/deletion

Reported by Gabriel Campana.

Closes #2764

Also changes the avatar from a jpeg to a png, to allow for
transparent background. The indexed png is also smaller in size.

Note that at the moment the default avatar is only used when
the user requested a custom avatar and the custom avatar file
is not found (should never happen).

In the future the default avatar could be used as a default
return when by-mail avatar lookups fail too (both gravatar
and libravatar support passing a default)

use 'official' repo.Name instead of incoming repoName; to enforce
correct capitalisation

Add start count corrector for Repository.NumClosedIssues

- Prevent panic on creating notice if database is not available
- Prevent incorrect folder on Windows ("/" instead of "\")

Fix #2872

Make user search function look in username (lower_name), full name
(full_name) and primary email (email). This will benefit searching after
user in "explore", admin panel and when adding new collaborators.

- Fix go-gogs-client#10
- Related to #809

Both are possible on explore and admin panel