[BUGFIX] Avoid PHP Warning  in Page Module

Change-Id: I218065a3445211d88ce131ecf23da3a947eb2e70
Resolves: #44540
Branches: 6.1, 6.0
Reviewed-on: https://review.typo3.org/17562
Reviewed-by: Mattias Nilsson
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer
Reviewed-on: https://review.typo3.org/17712
[BUGFIX] EM: un/install visual feedback

Adds a visual feedback to the un/install button action in EM:
Masks the extension manager during un/install operations
are in progress - after success a page redirect is fired.

Introduces a CSS class that class can be added to any link in EM:
.onClickMaskExtensionManager

Change-Id: If7aa0b15eeab1afb162b103662a10920f4da149f
Fixes: #43856
Releases: 6.0, 6.1
Reviewed-on: https://review.typo3.org/17091
Reviewed-by: Sebastian Michaelsen
Tested-by: Sebastian Michaelsen
Reviewed-by: Tobias Liebig
Reviewed-by: Mattias Nilsson
Tested-by: Mattias Nilsson
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer
Reviewed-on: https://review.typo3.org/17714
[BUGFIX] Correct TCA inclusion for uploads rendering

In the method that renders the uploads in css_styled_content
the call to load the TCA was replaced with its Frontend
counterpart to enable access to the configuration of custom
fields in tt_content.

Fixes: #44145
Branches: 4.5, 4.6, 4.7, 6.0, 6.1

Change-Id: I26f67fcfbf11db25c80ebe93ddd1e81167d828a9
Reviewed-on: https://review.typo3.org/17250
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer
Reviewed-on: https://review.typo3.org/17715