Extend conditional rendering in infoclick to allow if not statements

[jacobwod]

Current situation

As of #669 we can write something like:

{{if {foo}}}
Value of foo is:
{foo}
{{/if}}

and:

{{if {foo}="bar"}}
Value of foo is "bar", check it out:
{foo}
{{/if}}

We can also compare two attributes if we wish:

{{if {foo}={anotherAttribute}}}
Value of foo equals to anotherAttribute's value
{foo}
{anotherAttribute}
{{/if}}

This is not enough for cases where we want to see if a value does not equal to something.

Proposed solution

Let's introduce another operator, != that will evaluate to true if its left side does not equal to its right side.

All the examples above will work, we can compare to hard-coded text values as well as between two attribute values:

{{if {foo}!="bar"}}
Value of foo is not "bar", check it out:
{foo}
{{/if}}

The quotation marks around bar are optional. This works exactly the same:

{{if {foo}!=bar}}
Value of foo is not "bar", check it out:
{foo}
{{/if}}

We can also compare two attributes if we wish:

{{if {foo}!={anotherAttribute}}}
Value of foo does not equal to anotherAttribute's value:
{foo}
{anotherAttribute}
{{/if}}