Add partial support for "search=" URL parameter

Addresses #1875 according to the discussion in the thread.
This patch adds the URL parameter `#search=phrase`, with the following interpretation:
>Opens the Search UI and performs a search for the specified ~~word list~~ _phrase_ in the document. Matching words are highlighted in the document.
The ~~words~~ _phrase_ ~~must~~ _may_ be enclosed in quotes ~~and separated by spaces; for example:
#search=”word1 word2”~~

For reference, see http://partners.adobe.com/public/developer/en/acrobat/PDFOpenParameters.pdf#page=7