[enh] add user capacity to join/leave a course
Merge remote branch 'upstream/master'
[ref] add \n, limit lines at 79 chars
[ref] rename tree -> graph because it's more appealing
[enh] add document size in document list, in course show
[ref] remove stupid dependance to one of the worst python lib : pyPdf
[ref] remove debug message in processing_daemon
[fix] rename processing_daemon with the right orthography
[enh] add link to document viewer
[fix] rework the margin/padding default of contents, when navbar is down
[fix] make the links in #content blue
[fix] fix typo
[enh] add a first tryout of static viewer
[enh] make the thumbs image zone height dynamic
[enh] only load current seen image, not all at once in viewer
[fix] set the padding of the navbar really good
[enh] add navigation features in viewer
[enh] add zoom feature in viewer
[enh] list followed course in user's home
[enh] add persistance for navbar based on js cookies