[TASK] Boilerplate code of system environment system
[TASK] Move several system checks to new Check class

* checkMaximumFileUploadSize
* checkPostUploadSizeIsHigherOrEqualMaximumFileUploadSize
* checkMemorySettings
* checkPhpVersion

The implemented checks for memory settings and php version make the
ext:install/requirements.php file obsolete. The two tests are also
duplicated by the reports module and are removed for now. The idea
is, that the reports module gets an adapter to the new environment
check class later on to show *all* messages.
The check for minimum php version can be left out this way, too.
[TASK][Check] Better output of include path
[BUGFIX][Check] Fix return value of one status check
[TASK][Check] Provide HTML output for install tool status messages
Merge pull request #3 from maddy2101/check_for_lolli

[TASK][Check] Provide HTML output for install tool status messages
[TASK][Check] Add headline to status check module
Merge pull request #4 from maddy2101/check_for_lolli

[TASK][Check] Add headline to status check module
[TASK] Remove default files (DirectoryIndex)

Few default files are included in the directories typo3 and install
in case the server does not have the necessary DirectoryIndex.

Those can be removed since php is needed and DirectoryIndex
will include index.php in standard setup.

Change-Id: I5b5660b8f74242bd0924c89e105dee6dbb278fb8
Fixes: #45786
Releases: 6.1
Reviewed-on: https://review.typo3.org/18456
Reviewed-by: Wouter Wolters
Reviewed-by: Oliver Klee
Reviewed-by: Soren Malling
Tested-by: Soren Malling
Reviewed-by: Michael Stucki
Tested-by: Michael Stucki
[BUGFIX][Check] Fix a bug in includePath check, reduce severity to warning
[BUGFIX] Make backend user global available early

The global must be available very early, because methods below
might trigger code which relies on it. In particular the workspace
overlay of the rootline which is done in certain cases.

Fixes: #45625
Releases: 6.0, 6.1
Change-Id: I035f27e11cd56fc284442b66ad8357060f76e52c
Reviewed-on: https://review.typo3.org/18420
Reviewed-by: Mattias Nilsson
Reviewed-by: Oliver Klee
Reviewed-by: Helmut Hummel
Tested-by: Helmut Hummel
Reviewed-on: https://review.typo3.org/18487
[TASK][Check] Add more checks

Adds a trivial (and insecure) standalone version for cli for now

Implemented checks:
* max_execution_time
* disable_functions
* safe_mode
* doc_root
[TASK][Check] Add sql.safe_mode handling
[TASK][Check] open_basedir check
[TASK][Check] Implement suhosin checks from install tool
[FEATURE][Check] Add test for phar and vfs in suhosin.executor.include.whitelist
[TASK][Check] Add check for PHP opcode cache and doc comment reflection

A general test with warning severity is added if neither apc, xcache nor
eaccelerator is loaded.
The checks for working doc comment reflection from install tool
and a reports test in extbase are moved to a check method. This fails if
eaccelerator is not compiled with --with-eaccelerator-doc-comment-inclusion
flag and raises an error status now.
[TASK][Check] Improve wording of a test
[BUGFIX][Check] Fix broken header in install tool basic configuration
[TASK][Check] Move check for windows apache thread stack size