Adds functions for task manipulation based off of a given project

Get a list of subproject's IDs given a project ID
Get a list of tasks (in 3 arrays - urgent, other, normal) given a project ID
Changes project view to use the overview-style display

Table switched to a listing by deadline and keeps priority-based coloring
Moves HTML task addition to separate function

Allows for use inside project view without duplicate code
Fixes view selection on task deletion

Boolean can't be propagated properly, needs to be integer
Adds alert to notify user of failure if error text not present