Fix incorrect vertical spacing settings (fixes issue #27)

• new option ref
• new command \tasklabel

• prefer lazy boolean evaluation
• \tasksifmeasuringTF
• new option counter
• rename manual files

• \settasks' argument is now long, i.e., it allows a \par
• new option start for setting the starting value at which the list starts counting

The step to version 1.0 brought some significant changes:

• the option counter-format has been removed Labels can now be set quite similar to the way they are set in enumitem. This also made the enumerate option of the list template superfluous which has been removed accordingly.
• the commands \NewTasks and \RenewTasks have been renamed.
• the multiple choice lists have been removed.
• custom definitions can be put in a tasks.cfg file which is automatically loaded if available.