* rocketchat:postcss parser and cssnext implementation

* convert forms, keygrames and reset to cssnext

* convert rtl to cssnext

* convert base.less to cssnext

* convert base.less to cssnext

* fix * selector

* try to fix tests

* add css browser support

* remove duplicated test

* remove duplicated get

* skip fileupload test

* fix tests

* skip fileupload tests

* Try to fix tests

* try to fix the test

* test

* vai que vai

* fix wrong commit

* try again

* try some more

* try to fix tests

* skip the failing tests

* skip last test

* fix stylelint

* stylelint

* fix height calc

* skip sweetalert tests again

* skip more sweetalert tests

* [WIP] Igloczek styles cleanup (#5354)

* WIP: Styles architecture cleanup

* Fix build

* Move the reset to css on client

* moving some CSS from api.addAssets to api.addFiles

* moving more files to built time compilers

* Restoring clearfix

* moving more files to built time compilers

* moving more files to built time compilers

* move fontello to theme package

* Renaming files to preserve git history

* Renaming files to preserve git history

* using min to preserve history

* Fix lint

* organizing

* Renaming files to preserve git history

* Renaming files to preserve git history

* Fix lint

* Fix lint

* Renaming files to preserve git history

* Moving another less file to cue compiled at build time

* Fix lint

* Moving another less file to be compiled at build time

* adding some part of lesshat into temp mixings

* Put transitions back with some temp redundant mixing

* commenting out unused mixings

* removed unused mixings from lesshat

* Fix lint