Added support in daily tasks for specifying ’every X days’ and ‘every X weeks on specific days of the week’.

- shouldDo() now takes the entire task as an input instead of just the ‘repeat’ (days of the week) dictionary.
- the ‘start’ date for a task can be specified (and can also be in the future, in which case it will be greyed out until then.) ‘start’ date also affects ‘every X days’ and ‘every X weeks’.
- no migration code yet.

website/src/models/task.js

@@ -50,10 +50,14 @@ var checklist = [{
 
 var DailySchema = new Schema(
   _.defaults({
-    type: {type:String, 'default': 'daily'},
+    type: {type: String, 'default': 'daily'},
+    //TODO: Cleaner to store interval as enum instead of str?
+    frequency: {type: String, 'default': 'daily'}, // 'daily', 'weekly'
+    everyX: {type: Number, 'default': 1}, // e.g. once every X weeks
+    startDate: {type: Date},
     history: Array,
     completed: {type: Boolean, 'default': false},
-    repeat: {
+    repeat: { // used only for 'weekly' frequency, TODO: Rename to daysOfWeek or something with 'week'
       m:  {type: Boolean, 'default': true},
       t:  {type: Boolean, 'default': true},
       w:  {type: Boolean, 'default': true},