Folder search

Changes:

Add a "find folder" search button for finding folders in the folder list (or when selecting a folder for a copy/move operation). Granted, there already was a menu option for searching -- this just makes it much easier to access.  In response to <a href="https://github.com/k9mail/k-9/pull/200#issuecomment-9913526">comments on an earlier pull request</a>, a new "find folder" icon has been created for the search button, and a "Search for messages in all folders for the account" button has also been added that uses the existing search icon.
    
Eliminate the old-style search dialog boxes, and switch to using the action bar for folder searches.  This applies to folder searches initiated in both the FolderList activity and in the ChooseFolder activity

Provide a preference option that permits the user to enable the wrapping of folder names in folder list view. This is essentially a rebase of <a href="https://github.com/k9mail/k-9/pull/147">Pull Request 147</a>, so all the comments made there still apply.  The old pull request will be closed because it no longer applies cleanly to the current master.  The rebase of the old pull request has been included here in order to resolve a few conflicts between it and the other changes above.