Remove apt-get cleanup from Dockerfile

Purging/cleaning packages using apt doesn't actually reduce image size, and only creates additional layers, which doesn't add any benefit to the overall image.
Merge pull request #294 from ecnahc515/patch-2

Remove apt-get cleanup from Dockerfile
actually use SshPort variable

SshPort is defined (SSH_PORT) but the value is not actually used (just compared to default port 22).
Merge pull request #335 from taziden/patch-1

actually use SshPort variable
Revert "actually use SshPort variable"
Merge pull request #338 from gogits/revert-335-patch-1

Revert "actually use SshPort variable"
update dockerfiles README.md

typo
Merge pull request #365 from choas/patch-1

update dockerfiles README.md
Finish all new admin pages.
Removed trailing white spaces

Removed trailing whitespaces with

```sh
for file in `grep -r " $" * | cut -d : -f 1 | sort | uniq | grep -v " "`; do sed -i 's/[ \t]*$//' $file; done
```

and some handwork.
Merge pull request #394 from tstorch/trailing_white_spaces

Removed trailing white spaces
Update locale_zh-CN.ini

Double entry of "config.log_config"
Update locale_en-US.ini

Double entry of "config.log_config"
Update locale_de-DE.ini
Merge pull request #398 from fanningert/patch-3

Update locale_de-DE.ini
Merge pull request #397 from fanningert/patch-2

Update locale_en-US.ini
Merge pull request #396 from fanningert/patch-1

Update locale_zh-CN.ini
Merge branch 'master' of github.com:gogits/gogs into dev

Conflicts:
	dockerfiles/README.md
Add missing 'new migration' link

Addresses issue #399
UI: SSH/HTTPS address switch and copy