Use relative url when showing forked from

Add ability to delete single wiki pages.

Use hand-written SQL to do complex query

Render emojis in more places.

Repo setting to delete and disable wiki

- Remove unused config settings `[picture] service`

Set DefaultBranch to master when importing a new repo.

update README.md

ISSUE_TEMPLATE: suggestion to test at try.gogs.io

I've noticed that a lot of issues cannot be reproduced on http://try.gogs.io,
which either hints about specific database type problems or
hints about bugs which are already solved in the newer version
(as http://try.gogs.io is usually a newer build).

This patch adds the suggestion to test the issue at http://try.gogs.io in
the Github "issue template". The user can answer: "Yes", "No", "Not relevant".

"Not relevant" is an option where testing on http://try.gogs.io makes no sense as
the bug is unrelated to the Web UI or is very specific in nature.

- Migrate: #2704 #2653
- Clone: #2701
- Mirror, Pull

Hide the download archive button when viewing wiki pages

Change colour of numbers on pull request tabs if greater than zero

minor grammar fix

Improve test cases, config settings, also show SSH config settings on admin config panel.

allow native and ssh-keygen public key check

Add ForegroundColor for labels to resolve #2033

Image attachments keep aspect ratio