Update dom-bind template for Polymer 2

[alshakero]

As in move from

<template>
    <template is="dom-bind">
        ...
    </template>
</template>

To

<template>
    <dom-bind>
        <!-- `is` attribute is optional for Polymer 1 backwards compatibility -->
        <template is="dom-bind">
            ...
        </template>
     </dom-bind>
</template>

[warpech]

@PatrykSzwer can you pls do it? @alshakero will review.

[warpech]

After it is done please ping @ubbeK to release a new version of the extension.

[warpech]

Closing as done in #26

[warpech]

Release in Visual Studio marketplace is tracked in https://github.com/Starcounter/Starcounter.VisualStudio/issues/27

[warpech]

Can be marked as Finished when the extension is installable in Visual Studio (see https://github.com/Starcounter/Starcounter.VisualStudio/issues/27#issuecomment-356971462).