Pass minify config to jsminify task.

I would like to pass "mangle" and "squeeze" option to jsminify task. The change here allowing mojito app to have such config in application.json:

[
&nbsp;&nbsp;"settings": ["master"],
&nbsp;&nbsp;"shaker": {
&nbsp;&nbsp;&nbsp;&nbsp;"minify": {
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;"config": {
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;"mangle": true,
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;"squeeze": true
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}
&nbsp;&nbsp;&nbsp;&nbsp;}
&nbsp;&nbsp;}
]

As per my test on our app, this help reduce script size from ~310K to ~220K in our case.