Avoid capturing system/context settings in the TV list

[garryn]

Come across an issue where if there is a context or system setting in the Wayfinder tpls then it'll get incorrectly sucked into the tvList array.

This results in PHP warnings being logged (and can be numerous per Wayfinder call) basically along the lines of "Array key does not exist: +my_setting"

To fix this, I amended the regex in the findTemplateVars function in the Wayfinder class to be a bit more specific: ~\[\[\+([^\+]*?)\]\]~

Worked in my use-case but not sure if it needs anything more than that for general inclusion at this time.