Fix GROUP BY clause for PostgreSQL support

Use topological sorting to sort tables by dependency

Fix error checking

Add error checking for data import

Specify charset of XML file

Export supports both of XML and SQL

Export / Import as XML

Merge branch 'master' into mysql_support

(refs #1154)Fix path of request to the branch protection API

Fix solidbase version with 1.0.0

Remove PLUGIN table from export target

Fix solidbase plugin support

Update version and release document

Remove unnecessary files

Update pre-condition checking

Merge branch 'master' into mysql_support ...

# Conflicts:
#	src/main/resources/update/3_13.sql
#	src/main/scala/gitbucket/core/servlet/AutoUpdate.scala

Merge branch 'McFoggy-webhook-content-type'

Add Version 3.14

Merge branch 'webhook-content-type' of https://github.com/McFoggy/gitbucket into McFoggy-webhook-content-type ...

# Conflicts:
#	src/main/scala/gitbucket/core/service/WebHookService.scala
#	src/main/twirl/gitbucket/core/settings/edithooks.scala.html

Fix SQL for PostgreSQL

Display database url at the system setting console

Fixup

Fix table order in the exported sql file

Fix for PostgreSQL support

Update PostgreSQL configuration example

Remove unnecessary file

Use COALESCE instead of IFNULL

Merge pull request #1169 from McFoggy/issue-1168 ...

correct empty security token usage, fixes #1168

Add PostgreSQL support

Update MySQL configuration example