Introducing General::intval()

This method will insure that we are really dealing with a positive integer before trying to cast it.

This should eliminate nasty side effects like casting '1234a' to 1234.
Use General::intval to cast system:id

This will make it safer and should fix #2191
Added Status 302 header in redirect()

I do not know why, but without it, my setup was returning a 500 code if the actual http status was something else (404 in my case).

This fix only makes sure that the 302 status (temporary redirect) will be returned to the client.
After all, a call to redirect must really mean that we want a redirect.

Note: I did not used the Page class helpers since this is 'utility' code and I did not wanted to couple utility code to the Page class.
Better logic for handling http status codes

This change makes the error handler a little bit more smarter in the sense that it will try to extract the http status code from the exception it receives. If not status is found, then it reverts to the original implementation that was returning a 500.
Merge pull request #2222 from jensscherbl/integration

Fixed accidental output
Merge pull request #2199 from DeuxHuitHuit/redirect

Make the Error Handler smarter setting HTTP Status. Additionally send 302 Redirect in the redirect() utility function.
Merge pull request #2195 from DeuxHuitHuit/issue-2191

Filtering on the `system:id` using an invalid value will now return nothing instead of casting it blindly to an ID. Fixes #2191
Some cleanup of the Pages Editor
Simplify some of the backend page alerts.
Ensure prepopulation parameters persist even if an error occurs on initial entry creation. Fixes #2211
There isn't any need to use Reflection to get Event/Datasource data
Truncate entry titles when they exceed cell_truncation_length. Fixes #2224
Remove superfluous parameter, fixes #2216
Use the SYM_COOKIE_PREFIX for XSRF requests.
Release 2.5.2-rc.1
Offline js-fetch-sections DOM manipulations

When manipulating the DOM in order to add newly fetch data, the current implementation was causing some troubles in Chrome: Layout trashing was occuring between each append class into the select tag. While being inefficient, it was also causing visual glitches (See https://github.com/symphonycms/selectbox_link_field/issues/79).

The way to fix this is to "offline" those changes:

1. Detaching the select element from the DOM
2. Creating a detached list of all the option element
3. Append the detached list to the offline select element
4. Restore the select element to its original position
Removed unecessary translateZ hack

After much testing, this is not needed anymore for both latest Chrome and Safari.
In fact, there is now a penalty cost associated to it.
Fix indentation
New build
Merge pull request #2231 from DeuxHuitHuit/js-fetch-trashing

Offline js-fetch-sections DOM manipulations. Fixes symphonycms/selectbox_link_field#2231