Enable ESLint rule vue/no-use-v-if-with-v-for

[brianhelba]

https://eslint.vuejs.org/rules/no-use-v-if-with-v-for

The change here satisfies the rule, but also removes a somewhat awkward pattern where a v-for was being abused to set a temporary variable. The core issue the lack of a v-let syntax for setting scoped template variables (which is a requested feature). However, in removing the v-for abuse, we are forced to call findVectorProperty(filter) several times in the rendered template, which looks bad, but should be quite cheap (particularly in comparison to the amount of Javascript that's ultimately run in the Vue engine to render any parts of a template).