StiScanHistContainer: Use log scale for the vertical axis
Added track length to the HFT tree. Also added a corresponding histogram
StiScanHistContainer: Added a projection for the density profile
stiscan: Use user provided output directory to save images
Do not use a plus sign in the file names
Squashed commit of the following:

commit dded6be23abf63cb7708f97080343c5b3b02ca44
Author: Dmitri Smirnov <d.s@plexoos.com>
Date:   Fri Sep 5 16:23:19 2014 -0400

    Do not use a plus sign in the file names

commit 371bb6ec062a69bc2584c7319354661bab92d743
Author: Dmitri Smirnov <d.s@plexoos.com>
Date:   Fri Sep 5 16:21:13 2014 -0400

    stiscan: Use user provided output directory to save images

commit 7fc5954159abaf44b50f777f1cb495bec01e3ff5
Author: Dmitri Smirnov <d.s@plexoos.com>
Date:   Fri Sep 5 16:19:55 2014 -0400

    StiScanHistContainer: Added a projection for the density profile

commit 839befc16b7cfb1ffdb3b7ff7c94b2e6cec9db4d
Author: Dmitri Smirnov <d.s@plexoos.com>
Date:   Fri Sep 5 16:17:33 2014 -0400

    Added track length to the HFT tree. Also added a corresponding histogram

commit 5785c1d83ceb1f07e57252813314e543e01bf508
Author: Dmitri Smirnov <d.s@plexoos.com>
Date:   Thu Aug 28 13:41:51 2014 -0400

    StiScanHistContainer: Use log scale for the vertical axis
Merge branch 'ds'