Don't allow to save tasks without an assigned project

[jaragunde]

Every task should be assigned to some project. We must change this in two three levels:

• Frontend: the web UI shouldn't send tasks for save before the project field is set.
• Backend: tasks without a project shouldn't be saved. This affects third-party apps using the web services.
• Database: forbid null entries in the projectid field of a task row. If there are already any saved tasks with empty project ids, those should be migrated somehow. My first idea is to create a new project called "empty" and add those tasks there; then, the project "empty" can be checked to know who had empty project tasks and notify those users to reassign tasks properly.

[jaragunde]

Edited ticket description to add the "database" level.

[psaavedra]

@jaragunde, I need to know which is the database schema upgrade proccess and how works.

[psaavedra]

Related PR: #361

[jaragunde]

commit c238386d35cd712633e279fe39a0480c8bd99b72
Merge: bb8ccc9 88b5f20
Author: Jacobo Aragunde Pérez <jaragunde@igalia.com>
Date:   Wed Aug 23 11:16:19 2017 +0200

    [#351] Don't allow to save tasks without an assigned project
    
    Added controls to prevent this to frontend, web service backend and
    database.
    
    (Merge pull request #361)

commit 88b5f209806d2397f35672ce03f4303d56c5eb7d
Author: Jacobo Aragunde Pérez <jaragunde@igalia.com>
Date:   Wed Aug 23 11:09:39 2017 +0200

    Remove trailing whitespace and redundant comment lines

commit b384a709076b29e94e1cb33b94ae7a12c3a4843d
Author: Pablo Saavedra <psaavedra@igalia.com>
Date:   Wed Aug 16 15:21:19 2017 +0000

    Removed a trailing whitespace in createTasksService.php

commit e0d30227aca4709b4df59580da0f5b0d3e439d12
Author: Pablo Saavedra <psaavedra@igalia.com>
Date:   Mon Aug 14 16:09:59 2017 +0000

    Added SQL changes in the db schema

commit 8212a317924ded62aaad2e7d6d36f83cbcfecb99
Author: Pablo Saavedra <psaavedra@igalia.com>
Date:   Fri Aug 11 15:29:18 2017 +0000

    validateTasks in tasks.js also consider the projectComboBox

commit db2be051c12401f60eec10cd2f84afdd54425240
Author: Pablo Saavedra <psaavedra@igalia.com>
Date:   Fri Aug 11 14:39:32 2017 +0000

    createTasksService.php checks if projectId is sent

commit f7fe4359577e2f3eacd6ca9ddef403bf85eca6cd
Author: Pablo Saavedra <psaavedra@igalia.com>
Date:   Fri Aug 11 15:25:25 2017 +0200

    Tasks UI doesn't allow save before the project field is set

[jaragunde]

commit 28e8692833e8fcc5d8882456465ad303dac840de
Author: Jacobo Aragunde Pérez <jaragunde@igalia.com>
Date:   Wed Sep 6 11:07:35 2017 +0200

    [#351] Add restriction to new DB deployments
    
    Not null projectid restriction in the tasks table added to the
    database for new deployments.