use lowercase keys for internal structures
better model handling according to the context

Handling server-specific format in isEnabled() allows to use a single
function to load it from a file.
isolate configuration extraction for testing
better task interface

rename isEnabled() to getConfiguration(), and make it returns the task
configuration, instead of setting it, for testing purpose
no need for two distinct methods
perform all task configuration in a single place
no need for this warning anymore
simplification

The task->new(), task->configure(), task->run() model is simpler to
read.
standardize documentation
report execution failure
rename runRequestedTasks() to run()
rename _runController() to _runScheduledTasks()
fork once foreach controller, not foreach task

This reduce the number of forks, and avoid cluttering parent process
memory with the code needed for HTTP ocmmunication.
rename runTask() to runTaskIfScheduled()
better log messages
initial import
insert stylesheet reference in message

TODO: compute stylesheet path automatically
drop --html option
make html option as deprecated
local option is deprecated also