Dom cleaning

This a quite big PR that cleans the DOM from PointScope variables in order to avoid potential conflicts with other DOM elements. 

This PR touches the code structure and implies slight refactoring. In future versions, if an API has to be set up, a serious refactoring could be required.

Pointscope.html has been adapted to changes so that ongoing work can be done without loosing time. The main difference is that all DOM polluting variables are now scoped to PointScope.Object namespace:
- PointScope.Renderer: contains all objects and methods related to Three renderer
- PointScope.PsInterface: contains objects and method related to the GUI
- PointScope.Readers: contains all objects and method allowing to load/read data
- PointScope.Projections: projections parameters. Should by replaced in the next version by ajax request to projections server
- PointScope.Network: object and method relative data transfer protocols
- PointScope.Colormaps: colormaps for various point symbologies

This PR adresses issue #3 (https://github.com/mparkan/PointScope/issues/3).