Indiv task reminder: bug 1616

adds a checkbox to each task to indicate whether reminder is required.
This is especially useful if global setting is no, then selected tasks can be chosen for reminder.
Helps to avoid a flood of reminders for low level tasks.

on task add, the global setting is used as default.
The user can then use a checkbox to indicate whether he wants reminders or not.

The sql creates a new field in task table and presets with 0=no reminder for all tasks.
Can we load the sysval into a sql variable and then use that as default when creating the column?