Merge branches 'master' and 'testing' into testing
[s2p] changed location of the data directory to ~/s2p_demo_data
[s2p] rewrote the input_select method of the s2p demo

Symlinks are created in the working directory (self.work_dir), pointing
to the input data files (images, previews, rpcs)
minor change in lib/archive.py to allow archiving of files located in a
subfolder of the working dir.
[s2p] added upload feature
[s2p] minor change
[s2p] fixed paths issue
[sgm] add ground truth image in the result page
load only s2p, sgm, and orientation_modes demos
[sgm] changet git repo url in the build method
[sgm] updated xlink_article
[sgm] updated build method (links to scripts)
[sgm] add size_thresh param
[sgm] fix flipping-thumbnails loading
[sgm] changed default nb_iter and lr_thresh
[s2p] use potree.org 3D point cloud viewer instead of XB-pointstream
[s2p] size limit for upload is 100MB per dataset