moved array helper functions from jxg.js to utils/array.js
move type related helper functions into utils/type.js
collected most constants and moved them to base/constants

updated loadjsxgraph

temporarily deactivated the automatic search & load of jessiecode/jessiescript tags
move collectionContains back to the gui project, it is not used in JSXGraph and is just a wrapper for the isInObject/isInArray function.
move helper functions for numbers, strings and objects to separate files
Moved functions only used in browsers to utils/browser.js.
moved the jessiecode tag search/initialization to jsxgraph.js

This commit concludes the JXG.js split into several files:

* base/constants.js, constant values, e.g. COORDS_BY, OBJECT_CLASS, and OBJECT_TYPE
* utils/{array,number,string,object}.js for array/number/string/object related functions
* utils/env.js to detect the environment jsxgraph runs in (node, browser, metro app, desktop/mobile...)
* utils/browser.js for browser specific routines (CSS, browser events, position calculations)
* utils/type.js for type checking and conversions

JXG.js still exists, this file now has absolutely no dependencies; its sole purpose is to define the JXG namespace and hold a few basic functions (basically just extend, shortcut and debug plus temporarily getRef).