pgAdmin 4 commit: Allow to create sub-menu/menu-group by specify the sa

Allow to create sub-menu/menu-group by specify the same category in
multiple menu-items (not just the 'create' menu-group).

Moved all the main menu/context menu generation implementation in the
'menu' javascript menu.

In this implementation, if more than one menu-items specify same type
of categories, they will be created withing that group, otherwise - it
will be created separately (unless 'single' property of that category is
set to true).

We can also provide icon, priority, separator(s) above/below it for the
individual sub-menu too using pgAdmin.Browser.add_menu_category
function(...).

Branch
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master

Details
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http://git.postgresql.org/gitweb?p=pgadmin4.git;a=commitdiff;h=87f9834951f88e0068b9bc8e45dbf9007ad1094c

Modified Files
--------------
web/pgadmin/browser/static/js/menu.js | 259 ++++++++++++++++++++-
web/pgadmin/browser/templates/browser/css/node.css | 2 +-
web/pgadmin/browser/templates/browser/index.html | 17 +-
.../browser/templates/browser/js/browser.js | 225 +++++++++---------
.../browser/templates/browser/js/collection.js | 2 +-
web/pgadmin/test/__init__.py | 9 +-
web/pgadmin/test/static/js/test.js | 37 ++-
7 files changed, 397 insertions(+), 154 deletions(-)