Add ternary and setVar operations

[Michael-Gannon]

Added:

ternary - a {{ternary true "was true" "was false"}} operator
setVar - enable setting new variables on the context {{setVar "newVar" "var value" this}}{newVar}}

Together I've found using these like has cleaned up code that looked like this:

<span>
{{#if useRemote }}
<a class="title" href="/items/remote-"{{id}}>the item name</span>
{{else}}
<a class="title" href="/items/local-"{{id}}>the item name</span>
{{/if}}
<span class="desc">some description</span>
{{#if useRemote }}
<a class="callToAction" href="/items/remote-"{{id}}/>buy me now</item>
{{else}}
<a class="callToAction" href="/items/local-"{{id}}/>buy me now</item>
{{/if}}
</span>

** obviously this could itself have been a helper that specifically generated id's but I found I was creating HEAPS of little helpers, this simplified my life

To this:

<span>
{{setVar "itemId" (ternary useRemote (concat "remote-" id) (concat "local-" id) ) }}
<a class="title" href="/items/"{{itemId}}>the item name</span>
<span class="desc">some description</span>
<a class="callToAction" href="/items/"{{itemId}}/>buy me now</item>
</span>