Change rule format to allow rules to be written in JS

[pauljt]

So in pondering how we make more readable rules, I realized that if we can write rules in Javascript use a JS parser (e.g. acorn) to parse rules. This is a work in progress, but currently this PR makes the following changes:

• rules are now specified by a single javascript statement (rule.source)
• rule.source is parsed in an AST
• we test the AST to decide which rule template suits

This is awesome since it allows a bunch of cool features:

• you dont have to specify rule.type any more (this is determined from rule.source)
• template tests are now much easier to read:

member: {
      nodeType: "MemberExpression",
      test: function (rule, node) {
        var testNode=rule.statement.expression;
        if (node.property.name == testNode.property.name) {
          aw_found(rule, node);
        }
      }
    },

• using JS source to specify rules allows for richer rule types. This allows more complex rules, like the callwithargs template, which checks the the literal arguments to a function, and only matches if the function name matches AND all the literal arguments match (respecting order)

I'm just refactoring the new rules to use this format, then this will be ready to go.

[pauljt]

All rules refactored. Separate tests now for production and test rules. Just needs a little bit of UI cleanup, and maybe a readme update, and this will be ready to merge.

[mozfreddyb]

I get "error parsing nfc manager permission. the test is empty for source, testhit and testmiss. According to https://bugzilla.mozilla.org/show_bug.cgi?id=952217#c17 the patch that landed doesn't make it so easy to test if something has nfc-manager, but I'm not sure I get it. Removing this makes things work ;)

The Experiment tab doesn't work completely: We need a button since I find the onkey-thing for the rule field unintuitive :)

[mozfreddyb]

Also client/js/rules.js is somehow broken, the check for localStorage exists but everything using localStorage is outside of this. I dont know how this happens but I will fix this separately from this.

[pauljt]

Re the empty rule. You get an error, but it still works - the rule parser is error tolerant I hope. THe reason for this is nfc is a difficult permission to scan for. We can remove it for now though.

The experiment tab does work completely, its your brain which is broken ;) But yeh I can add a button if you want.

Actually rule.js and scan.js are basically ready to be removed. My plan was once this is landed, to add a seperate patch which remove the old scan.js and rules js, and renames AcornWalker.js to scan.js

Make sense?