[TASK] EXT:form - Use unique ids for multiple forms

Use consecutive ids if more than one form is present on a page.

Resolves: #70211
Releases: master
Change-Id: I2d5f2f27290923ec4c6eaf3ccb06e4ad41815bd3
Reviewed-on: http://review.typo3.org/43750


Reviewed-by: Daniel Goerz <ervaude@gmail.com>
Tested-by: Daniel Goerz <ervaude@gmail.com>
Reviewed-by: Bjoern Jacob <bjoern.jacob@tritum.de>
Tested-by: Bjoern Jacob <bjoern.jacob@tritum.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>