* Makes network eslint compliant
Unused variables in private functions, who were never called internally with those arguments were removed.
lint rule was disabled for public functions, and in private functions which were called internally with those unused arguments

* Disables linting for unused args passed into DataSet and DataView

Fix for #3164

- `network.clustering.cluster()` now handles all nodes, not just the visible ones
- Changing ivisibility of nodes now explicitly takes clustering into account, see `Network._updateVisibleIndices()`
- `network.clustering` does not change `hidden` status any more.

The important part of this PR is the realization that 'hidden' and 'clustered' are two distinct things and should be handled separately.
In particular, clustering should **not** change the `hidden` state in any way.

* clusters in hierarchical working for sortorder 'hubsize'

* Code cleanup

* replacing all ES6 imports with CJS require calls
resolves #2934
used the following regex to apply the changes in lib:
s/import\s+(\w+)\s+from\s+(.*);\s*$/var $1 = require($2).default;/
s/import\s+(\w+)\s+from\s+(.*)\s*$/var $1 = require($2).default;/

* cleaning up inconsistencies

added example. Improved handling of options for hierarchical view.

- Fixed #1528, #1278, avoided ID's being cast to string for methods that return ID's as well as storePositions casting to string.

Missed "apply" call on DOMtoCanvas call

- Added beginnings of unit testing for network.