Use custom expression parser instead of babel to template expression

[pmdartus]

Description

Currently, we are using babel to parse and validate template expressions. We used it originally to avoid having to implement a custom expression parser for now. We are seeing currently 2 types of issues with using babel.

• The compiler throws a cryptic error message when the expression is valid javascript but isn't a valid template expression.

<template>
    <div>
        h1 { color: red }
    </div>
</template>

• The compiler throws when using javascript keywords

<template>
    <div class={class}></div>
</template>