Add eslint support

Here is an attempt to support `eslint`.
The file `.eslintrc` defines the rules. Usually the value are :
* 0 : do not check
* 1 : warn
* 2 : fail

I have integrated the eslint check in the gulp `static` task.
I have fixed a few files to comply with eslint warnings or errors.

Let me know if you find it usefull

Avi

yep, should have been caught by eslint, changing the config file so it now will be