Update orgchart library dependency to latest one

[paodb]

Currently, Orgchart Add-on is relying on a very old version of OrgChart library, 2.1.4. Checking the library repository, the latest at this moment is 3.6.0. There a few updates regarding not longer depending on the use of font-awesome for icons, some changes on the display of export button, some refactoring, dependencies updates and more.

It will be nice to make the add-on rely on a newer version and also to check if it could help to fix some identified issues this add-on is currenty presenting/causing (#65, https://github.com/FlowingCode/AddonsDemo/issues/103, #72).

[paodb]

I did a test using the latest version and I can see some changes but not significant ones, for example, if I compare the first example in the demo, in the current version of the add-on it looks like this:

When updating the library sources, the export button displays on bottom, thestyling of the nodes seems better, the icons are different:

I see some problem on the display of the Bottom to Top example:

Current:

With the update:

I still need to run more testing and see what updates are needed in the add-on (for example regarding fc-orgchart.js).

One good thing about this is that the export no longer breaks as reported in #65 but the problems reported in https://github.com/FlowingCode/AddonsDemo/issues/103 & #72 remain.