improve the serialization of custom user models

(cherry picked from commit 7b34eabe4b506c3e49e4dedbefee66c1612bb83d)
[#3307] Adding an additional note about deserialization issues

(cherry picked from commit 7325ec5044c0339275a9700e767d88707116f79d)
[#3307] Fix thanks to @xabbuh

(cherry picked from commit 38612bc190ab2f97f2fbd3f3bc18a591df153cbe)
Clarifying some details on serialize/unserialize and making it consistent with changes we recently made

(cherry picked from commit f285c5a572ee88e94a9314e152a5075243811d49)

Conflicts:
	cookbook/security/entity_provider.rst
Changed sha1 into bcrypt
[#3356] Fixing ticks that don't work inside a bold and removing extra details in intro area that aren't necessary (you'll need to read the cookbook entry for more details anyways)
[#3356] Changing to use the bcrypt algorithm

Also removing one example (now possible with using bcrypt from the beginning) and related tweaks.
[#3356] Moving serialize and Equatable logic further down for clarity
[#3356] Clarifying when you need a salt

Also filling in other details related to using BCrypt
[#3357] Many many changes thanks to @WouterJ and @xabbuh
Merge pull request #3357 from symfony/security-2914-additions

New Security Authentication Additions
Merge pull request #3359 from xabbuh/fix-build-errors-2.3

[Components][Form] fix code block indentation
Merge pull request #3361 from xabbuh/fix-build-errors-2.4

[Components][DomCrawler] adding XML code block
Merge pull request #3362 from unairoldan/patch-1

Update composer installation command
Merge branch '2.4'
[#3362] Updating composer install version on the master branch
Merge pull request #3365 from evilr00ts/patch-1

Update process.rst
clarify that password is shown only upon submission
Documentation should refers to @Security and no @Secure
Fixed SensioFrameworkExtraBundle complete name