Implement our own Drawer instead of relying on an third-party dependency

In Flamingo, we use http://git.blivesta.com/drawer/ for the main menu.

However, we have a critical bug in it: XWIKI-13135.

I've tried to upgrade the drawer to the last version, but it was not very stable and we had a lot of failures on the functional tests.

Moreover, the team seems to not communicate very well: no release notes, no answer to github issues, etc...

Examples:

• https://github.com/blivesta/drawer/issues/23
• https://github.com/blivesta/drawer/issues/21

So I've tried to get rid of this and I made a prototype of a more simple drawer.

Results are there: https://jsfiddle.net/k68t1L31/

If you are OK with this, I'll do in platform.