Remove the logfile and logSize columns from the database

It's pointless to store these, since Nix knows where the logs are.
Also handle (in fact require) Nix's new log storage scheme.  Also some
cleanups in the build page.

src/lib/Hydra/Helper/AddBuilds.pm

@@ -17,7 +17,7 @@ use File::Temp;
 our @ISA = qw(Exporter);
 our @EXPORT = qw(
     fetchInput evalJobs checkBuild inputsToArgs captureStdoutStderr
-    getReleaseName getBuildLog addBuildProducts restartBuild scmPath
+    getReleaseName addBuildProducts restartBuild scmPath
     getPrevJobsetEval
 );
 
@@ -27,16 +27,6 @@ sub scmPath {
 }
 
 
-sub getBuildLog {
-    my ($drvPath) = @_;
-    my $logPath = ($ENV{NIX_LOG_DIR} || "/nix/var/log/nix"). "/drvs/" . basename $drvPath;
-    return $logPath if -e $logPath;
-    $logPath = "$logPath.bz2";
-    return $logPath if -e $logPath;
-    return undef;
-}
-
-
 sub getStorePathHash {
     my ($storePath) = @_;
     my $hash = `nix-store --query --hash $storePath`
@@ -930,7 +920,6 @@ sub checkBuild {
                 , buildstatus => -f "$outPath/nix-support/failed" ? 6 : 0
                 , starttime => $time
                 , stoptime => $time
-                , logfile => getBuildLog($drvPath)
                 , errormsg => ""
                 , releasename => getReleaseName($outPath)
                 );