TinyMCE plugin breaks the package in Plone 5

When trying to start Plone with this package installed the following exception is shown:

```python
$ bin/instance fg
2017-01-06 17:20:56 INFO ZServer HTTP server started at Fri Jan 6 17:20:56 2017
Hostname: 0.0.0.0
Port: 8080
/home/hvelarde/.buildout/eggs/plone.app.dexterity-2.3.2-py2.7.egg/plone/app/dexterity/__init__.py:12: DeprecationWarning: Name clash, now use '_' as usal. Will be removed in Plone 5.2
DeprecationWarning)
/home/hvelarde/.buildout/eggs/plone.app.multilingual-4.0.3-py2.7.egg/plone/app/multilingual/browser/migrator.py:11: DeprecationWarning: LanguageRootFolder: LanguageRootFolders should be migrate to DexterityContainers
from plone.app.multilingual.content.lrf import LanguageRootFolder
/home/hvelarde/.buildout/eggs/plone.portlet.collection-3.1-py2.7.egg/plone/portlet/collection/collection.py:2: DeprecationWarning: isDefaultPage is deprecated. Import from Products.CMFPlone instead
from plone.app.layout.navigation.defaultpage import isDefaultPage
...
File "/home/hvelarde/.buildout/eggs/zope.configuration-3.7.4-py2.7.egg/zope/configuration/config.py", line 179, in resolve
mod = __import__(mname, *_import_chickens)
File "/home/hvelarde/.buildout/eggs/Products.TinyMCE-1.4.3-py2.7.egg/Products/TinyMCE/browser/controlpanel.py", line 7, in
from plone.fieldsets.fieldsets import FormFieldsets
zope.configuration.xmlconfig.ZopeXMLConfigurationError: File "/home/hvelarde/collective/sc.embedder/parts/instance/etc/site.zcml", line 16.2-16.23
ZopeXMLConfigurationError: File "/home/hvelarde/.buildout/eggs/Products.TinyMCE-1.4.3-py2.7.egg/Products/TinyMCE/configure.zcml", line 15.2-15.32
ZopeXMLConfigurationError: File "/home/hvelarde/.buildout/eggs/Products.TinyMCE-1.4.3-py2.7.egg/Products/TinyMCE/browser/configure.zcml", line 11.4-16.10
ImportError: No module named fieldsets.fieldsets
```

this happens because Products.TinyMCE is no longer a dependency of Plone.

we need to decouple the plugin registration so we can handle it in different forms.