Move account level web hook settings to account settings

Update CSS

fix .travis.yml ...

- install java9 explicitly https://github.com/travis-ci/travis-ci/issues/7944
- restore main java8 build (bug or change specifications? https://twitter.com/xuwei_k/status/873104018100244480 )
- "sudo apt-get install libaio1" fail. use apt addons https://github.com/travis-ci/apt-package-whitelist/pull/3698

(refs #1620) Bump AdminLTE to 2.3.11

Merge pull request #1488 from kounoike/pr-add-account-webhook ...

Add account(group/user)'s webhooks feature.

Fix compilation error

Merge branch 'master' into pr-add-account-webhook

Merge pull request #1616 from imeszaros/issue-priorities ...

Issue priorities

Eliminate manual emtpy to none conversion. This may close #1396

Having a default priority is now optional.

Show errors related to priority description.

Priority description is now optional.

Prefer external styles instead of inline.

Default priority feature implemented.

Added the 'is default' column to priorities table.

Fix: added handling of priorities on repository rename/delete.

Default priorities changed according to the wishlist spec.

Priorities now have a description that appears as a standard HTML ...

tooltip across the app.

Priorities now integrated with issues.

Added foreign key to issue table, extended the issue outline view to ...

include the priority.

Priorities CRUD interface implemented.

jQuery UI sortable plugin added to the app.

Added model classes for priorities.

Added table for priorities.

Merge remote-tracking branch 'origin/kounoike-pr-sidebar-mini'

fix sbt version when oraclejdk9 test

Merge pull request #1615 from gitbucket/feature/plugin-notification ...

Add hook for issue and pull request

Implement existing email notification using plugin hooks.

Fixup

Show icons when sidebar is collapsed.