Pull request for linkout repairs

[ekcannon]

• Several repairs to linkouts. I don't expect these to impact other instances, but please check. The most frustrating issue was the GBrowse linkouts. The GBrowse URL construction requires parameters within parameters and I couldn't find a way to convince l() to not URL-encode the sub-parameters. I added copious notes to blast_ui.linkouts.inc describing the problem and anyone is more than welcome to have a go at finding a better way than brute-force construction of the link.
• The prompt for the target select dropdown was appearing at the bottom of the options. PHP's weirdness in making all arrays associative. I discovered a trick, using '+' to prepend the prompt to the option list without changing any keys.
• Default for # threads is 1.
• Very minor cosmetic changes to prompt text.

[laceysanderson]

Ethy, I see this pull request is automatically updating (little known "feature" of github; see note below) so I'm going to wait to look at it until you give me the Okay.

Note that when creating pull requests, the changes should be on a separate branch (not your repo main branch) because any changes to the original branch will be incorporated into the pull request. This is meant to allow updating a pull request based on maintainer requests :-) If you naturally develop on your main branch simply create a branch specifically for the pull request from the main one and then use that branch (which is an exact copy at this point) for the pull request.

[ekcannon]

I am going to reject this pull request because the admin page in this version includes the option to turn on web services even though the advertised change was to the generic linkouts. The web services are not fully functional, so they and the generic linkout fix will be offered in a later pull request.