Gruntfile: add task for mirroring sources to github
feat(build) do not include functions for HTML-based script into JS-based

Running long-standing loops in HTML-based scripts may cause a UI freezes
and other side effects. To fix that we need to call `Host.CanContinue()`
method every 5 seconds (not sure about interval duration). However that
call is useless in JS-based scripts. In this commit we add support of
custom marker that can be replaced with text/code that is correspondent
to current type of build script

See issue #9 for details
fix(core) deal with 'Host.CanContinue()' in core stuff
refactor(dispatcher): move global method inside Dispatcher class

We used to have a 'isScriptAllowedToRun()' method which returns either
true or false that allow or not to run particular script. Since process of
run of the script is happen inside a Dispatcher class we move that
method also to Dispatcher class.
style(definitions): add comment, remove useless spaces
fix(ext|autoscope) replace 'Host.CanContinue()' with proper macros
fix(ext|math-helper) replace 'Host.CanContinue()' with proper macros