hydra-queue-runner: don't clutter the system log with debug message

Avoid the frequently printed

  hydra-queue-runner[10293]: system type `x86_64-linux': 2 active, 2 allowed, starting 0 builds

message. That information is only interesting when some build are
actually started.
Fix showing build steps in the machine status page

This was broken because of the comparison

  step.machine.match('@(.*)').0 == m.key

where m.key contains the SSH user.

Also some style tweaks.
Machine status: Don't show removed machines anymore

This requires a sequential scan on the BuildSteps table, which by now
takes > 8s.
Remove some redundant SQL queries
Make negative narinfo responses much smaller
Minor tweak
Allow searching for store and drv paths. Only does a complete match to reduce load on database.
getPrimaryBuildsForView: Return all view results

Returning only the first 20 results can cause NixOS/Nixpkgs channel
generation to fail, if the first 20 view results correspond to
evaluations that haven't finished yet.  Then URLs like
/view/nixos/tested/latest-finished will return 500 rather than the
latest finished view.
When searching a path / drv path, use separate queries for both options to prevent seq. scan.
Ellipsize long jobset/job names to prevent bootstrap navbar breakage
Don't do <tt> on input type
Remove unused file
makeLink -> menuItem
Add some gitignores
Use bootstrap's pager (instead of pagination) class
Update bootstrap to 2.3.1
Remove tablesorter

We haven't used it for a while now.
Remove project/jobset/job/build id from the navbar

They take up too much space, and they're visible in the page title
anyway.  But include them as a nav-header in the submenus.
Use the default navbar style for readability
Use a popover to show how to use the build reproduction script