[BUGFIX] Frontend Login not added to CSC anymore

As felogin has no dependency for CSS Styled Content
it registers itself via
ExtensionManagementUtility::addTypoScript()
and does not hook in after css_styled_content, because
CSS styled content itself hasn't been initialized at that
time. Thus, felogin needs to have a dependency on
css_styled_content in order to still work as before.

Additionally, some unnecessary TypoScript code
was removed / cleaned up at the same time.

How to reproduce:
Add a login CE and you'll get a yellow error
message. Apply the patch, and the form will
show up (you need to uninstall / install an
extension first in order to have the dependecy
resolving take place).

Releases: 6.2
Resolves: #55557
Change-Id: I81e590038c10e793538419523ba37d3b29700b48
Reviewed-on: https://review.typo3.org/27233
Reviewed-by: Christian Kuhn
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Stefan Neufeind
Tested-by: Stefan Neufeind