* Add support for federated avatars

Fixes #3105

Removes avatar fetching duplication code
Adds an "Enable Federated Avatar" checkbox in user settings
(defaults to unchecked)

Moves avatar settings all in the same form, making
local and remote avatars mutually exclusive

Renames UploadAvatarForm to AvatarForm
as it's not anymore only for uploading

* Run gofmt on all modified files

* Move Avatar form in its own page

* Add go-libravatar dependency to vendor/ dir

Hopefully helps with accepting the contribution.
See also #3214

* Revert "Add go-libravatar dependency to vendor/ dir"

This reverts commit a8cb93ae64.

* Make federated avatar setting a global configuration

Removes the per-user setting

* Move avatar handling back to base tool, disable federated avatar in offline mode

* Format, handle error

* Properly set fallback host

* Use unsupported github.com mirror for importing go-libravatar

* Remove comment showing life exists outside of github.com

... pity, but contribution would not be accepted otherwise

* Use Combo for Get and Post methods over /avatar

* FEDERATED_AVATAR -> ENABLE_FEDERATED_AVATAR

* Fix persistance of federated avatar lookup checkbox at install time

* Federated Avatars -> Enable Federated Avatars

* Use len(string) == 0 instead of string == ""

* Move import line where it belong

See
https://github.com/Unknwon/go-code-convention/blob/master/en-US/import_packages.md

Pity the import url is still the unofficial one, but oh well...

* Save a line (and waste much more expensive time)

* Remove redundant parens

* Remove an empty line

* Remove empty lines

* Reorder lines to make diff smaller

* Remove another newline

Unknwon review got me start a fight against newlines

* Move DISABLE_GRAVATAR and ENABLE_FEDERATED_AVATAR after OFFLINE_MODE

On re-reading the diff I figured what Unknwon meant here:
https://github.com/gogits/gogs/pull/3320/files#r73741106

* Remove newlines that weren't there before my intervention

- Try to reduce memory allocations
- Add possibility to disable diff highlight (can improve performance for large diffs)
- Tweaking with cost for prettier (cleaner) diffs
- Do not calculate diff when the number of removed lines in a block is not equal to the number of added lines (this usually resulted in ugly diffs)

Enable/disable input based on user chosen options for wiki and issue tracker.

* Add MaxDisplayFileSize setting

* Don't show files that are too large

* Localized FileTooLarge

* Change IsFileTooBig => IsFileTooLarge

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.

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

QQ STMP host port is 465

host = smtp.qq.com:465

and need the Authorized

"is activate" -> "is activated"

Closes #2764

As you included Czech translation to official distribution, I think I'm missing here.
I know, selfish as hell... ;)

Always send user to settings screen to change avatar.
Drops "change_custom_avatar" localized message, keeps "change_avatar"
for the generic one.

NOTE: only changes the en-US locale, as per
https://github.com/gogits/gogs/wiki/Contributing-Code#those-we-do-not-accept

NOTE: requires rebuild of bindata.go to fully see effects

- Update language choose dropdown to fit more languages

Prevent `Forgot Password` for non local users