Add support for multiple identifier lookup to the magic wand tool.

This does two things:

1) It allows entering multiple identifiers into the magic wand tool for simultaneous lookups. The identifiers do have to be of the same type.

2) When pasting text with multiple lines, it expands the magic wand tool into a multiline textbox to allow for easier navigation and editing. This also means that pressing enter when in the multiline mode inserts a new line instead of submitting a result. To overcome this limitation, a search button appears when in the multiline mode.

Some discussion here: http://forums.zotero.org/discussion/12673/add-multiple-items-by-identifier/
Also related http://forums.zotero.org/discussion/24111/