Currently FTL files are cached for 5 seconds when they are requested. In developer mode this should be removed to improve developer experience of the responsiveness of Magnolia to their changes. This will also enable using a "hot browser reload" mechanism like BrowserSync or LiveReload.

Symptom:
Change an ftl file. Refresh the webpage and see the change instantly.
Change the ftl file again. Refresh the webpage before 5 seconds elapsed and you will not see the change. Only after 5 seconds have elapsed since the last change was rendered will the new change be rendered.

Notes:
freemarker.cache.TemplateCache sets the default refresh delay to 5s

The 'FTL lock' problem is solvable by doing this at L123 in FreemarkerHelper:

 cfg.setTemplateUpdateDelay(0);

As this change will negatively impact performance, it should only be appllied when developer mode is enabled.

Documentation:
Please document also in a section about all the changes that developer mode activates.