New config setting to disable Creation of real time segments by non Super Users

[mattab]

Use case: browser archiving is disabled, but users can still create Segments processed in real time.

When users create segments this can add huge load on the database servers, especially if users create lots of segments or if the websites tracked are huge.

Task:

• Let's add a new config setting, that will allow a piwik admin to disable the feature of Real time segments.
• When this setting is enabled, all Segments created after this setting was enabled, will only show the option for "Pre-processed". Users will not be able to create real time segments.

See also: #4569

[mattab]

In fa04cb4: fixes #4675 Adding new config file setting:

; By default, users can create Segments which are to be processed in Real-time.
; Setting this to 0 will force all newly created Custom Segments to be "Pre-processed (faster, requires archive.php cron)"
; This can be useful if you want to prevent users from adding much load on the server.
; Note: any existing Segment set to "processed in Real time", will still be set to Real-time.
; this will only affect custom segments added or modified after this setting is changed.
enable_create_realtime_segments = 1