Fix typos, add notes on attribute prefixes.

[arthurevans]

I believe both instances of "event" here were typos... Also added some details on "attribute name" after looking at the default template processor implementation.

Even with this change, I do not understand the description of the "strings" argument:

• @param strings The string literals. There are always at least two strings,
  event for fully-controlled bindings with a single expression.

• "the string literals"--which string literals. Where are they coming from? Why does the default template processor mostly throw them away?
• "there are always at least two strings"--why?
• "fully-controlled bindings"--we've never defined this term, and I don't know what it means.

I think most of these questions would be clarified by an example. "For example, with a simple binding like foo=${bar}, the literals would be ..."

I know this is kind of an internal class, and maybe doesn't need the highest level of doc, but this one seemed extra cryptic.

[justinfagnani]

@param strings The string literals. There are always at least two strings,
event for fully-controlled bindings with a single expression.

"the string literals"--which string literals. Where are they coming from? Why does the default template processor mostly throw them away?

The string literals are the string parts of a template literal expression. In

html`a${b}c`

The string literals are ['a', 'c']

"there are always at least two strings"--why?

In

html`${b}`

The string literals are ['', '']. There are always num_expressions + 1 string literals. Since we always have at least one expression by the time we call this method, there are always two string literals.

"fully-controlled bindings"--we've never defined this term, and I don't know what it means.

This means a binding that takes up the whole attribute or property value, like a=${foo} or a="${foo}". In this case we're not going to do a string interpolation, but just pass the value to setAttribute() or assign to the property. We detect this case from the string literals being ['',''].

Hope that helps!

[arthurevans]

Updated, @justinfagnani PTAL.