hydra: buildmachine disabled by default, add some default constraints

Dependencies

• [2] SMCOU72F hydra: add some admin for adding/enabling/etc build machines
• [3] ZWCTAZGL added newsitems, added some admin options to clear various caches.
• [4] 2M7J26V4 inital version of links to diff in scm
• [5] QT4FO2HP refactored admin controller, using chains, to avoid using requireadmin on each endpoint
• [6] D5ZR3ZY6 hydra: missing property
• [*] N22GPKYT * Put info about logs / build products in the DB.

Change contents

• replacement in src/lib/Hydra/Controller/Admin.pm at line 149
  [2.4583]→[2.4583:4647](∅→∅)
  − my $hostname = trim $c->request->params->{"hostname"};
  [2.4583]

  [2.4647]
  + my $hostname = trim $c->request->params->{"hostname"};
• replacement in src/lib/Hydra/Controller/Admin.pm at line 155
  [2.4860]→[2.4860:4908](∅→∅)
  − updateMachine($c, $machine);
  [2.4860]

  [2.4908]
  + updateMachine($c, $machine);
• edit in src/lib/Hydra/Controller/Admin.pm at line 157
  [2.4916]

  [2.4916]
  + saveNixMachines($c);
• replacement in src/sql/hydra.sql at line 490
  [2.12468]→[2.12468:12550](∅→∅)
  − username text NOT NULL,

  − ssh_key text NOT NULL,

  − options text NOT NULL,
  [2.12468]

  [2.12550]
  + username text DEFAULT '' NOT NULL,

  + ssh_key text DEFAULT '' NOT NULL,

  + options text DEFAULT '' NOT NULL,
• replacement in src/sql/hydra.sql at line 495
  [2.12640]→[2.12640:12679](∅→∅)
  − enabled integer DEFAULT 1 NOT NULL
  [2.12640]

  [3.864]
  + enabled integer DEFAULT 0 NOT NULL