Add setting.AppSubUrl in case of different ROOT_URL and LANDING_PAGE = explore

HTML tags are no longer processed for special links, etc
Contents of <a>, <code> and <pre> are not processed for special links
Processing for special links is done after Markdown conversion

- modules/middleware/context.go: add HandleAPI method

- routers/user: little code format
- conf/locale: update French locale

The normal go get protocol is to show the go-import meta tag when ?go-get=1 is appended to the url. This commit implements that behaviour and cleans the go-get option from the repository settings page.

The "PHP" formatting function doesn't add anything, except an undocumented date format.

All usages in the templates have been replaced with DateFmtShort and DateFmtLong for convenience.

The boolean flags in the repo context have been replaced with mode and two methods

Also, the permissions have been brought more in line with https://help.github.com/articles/permission-levels-for-an-organization-repository/ , Admin Team members are able to change settings of their repositories.

New config keys in [mailer] section:
 - CERT_FILE: path to a certificate file.
 - KEY_FILE: path to a key file.

This commit does a lot of the work of refactoring the access table in a table with id's instead of strings.

The result does compile, but has not been tested. It may eat your kittens.

Fixes #921 and makes the Mention regexp be in line with the others

- modules/base/markdown.go: fix issue link issue
- routers/repo/view.go: remove useless code

- conf/locale: add mew translator profile

This commit does a lot of the work of refactoring the access table in a table with id's instead of strings.

The result does compile, but has not been tested. It may eat your kittens.

- routers: use new binding convention to simplify code
- templates: able to set HTTP port number in install page

- update russian locale