Support for path traversal

[pascalbaljet]

This PR brings to support path traversal, for example, in the <Link> component. This behavior matches how regular <a> tags work.

For example, if you're on http://app.test/users/1/edit/, you can now use relative dotted syntax like:

<template>
    <Link href="../">User 1 Profile</Link>
    <Link href="../../">Users Index<Link>
    <Link href="../delete">Delete User 1<Link>
</template>

Note how the original URL has a trailing slash. Again, that's how it works with regular <a> tags. Fixes #1917.