task.py: use a short basename for output files

When storing the files in the db, web2py adds an hash.
There is no need to have a hash in the original filename (and it can produce files with too long filenames).
js/builder.js: warning/alert when the ratio of segmented reads is below some thresholds
css: warning/alert, css
js/model.js: parse_error when there is an exception in parseJsonData()
com.js: factorize BUTTON_CLOSE_POPUP + reindent code
com.js: align_error wording

Even if the user is on the net, the server can be down...
model.js: loadClusters() works if 'clusters' is not defined
com.js: do not ouput messages to console if priority < min_priority_console
js/: by default, do not display on console detailed timings