Cache calls to htmel

[lefetmeofefet]

Calling htmel a lot of times can become slow, especiall if we're updating a list frequently, causing the whole list to be calculated and each item in the list calls htmel.
Caching will save the extra time of processing the template. Basically, the flow is:

• htmel is called, check if cache contains the state object
• if contains, clone the existing template
• otherwise create a new template, and save to cache