Merge branch '425-extension-download-links-should-have-rel-nofollow-or-be-excluded-via-robots-txt' into 'develop'

Resolve "Extension download links should have rel="nofollow" or be excluded via robots.txt"

Closes #425

See merge request t3o/ter!488

[BUGFIX] Deliver WSDL with /ter?wsdl

See merge request t3o/ter!497

The SOAP endpoint does not deliver the WSDL file when using
the common ?wsdl GET parameter.

This is now added, allowing to use

http://extensions.typo3.org/ter?wsdl=1

in addition to:

https://extensions.typo3.org/typo3conf/ext/ter/tx_ter_wsdl.php

to conform standards (which are also necessary for the tests)

Cleanup of tx_ter_helper

See merge request t3o/ter!496

checking all extensions with foreach

* Use Doctrine instead of legacy db connection
* Add types to variables and returns
* Simplify functions
* Remove unused code

[TASK] Remove more unused functionality from EXT:ter

See merge request t3o/ter!495

[TASK] Remove unused code in TER API and use modern APIs

See merge request t3o/ter!494

* ext_autoload is not needed anymore, as it is loaded via composer.json
* tx_ter_helper->getLatestVersionNumberOfExtension is not in use anymore
* and the tx_ter_extensionmembers.gif icon was not removed in the previous commits

* The Configuration/ExtConf PHP class is never used and removed
* the file Command/TerCommand is empty and removed
* All plugin registration of ext_tables.php is moved to Configuration/TCA/Overrides
* Unused "locallang.php" is removed

[!!!][TASK] Refactor generation of extensions.xml.gz

See merge request t3o/ter!491

The tx_ter_api class is cleaned up as follows:

* Use PSR-3 logging mechanisms instead of TYPO3_DLOG constants
* Remove reference to cObj as it is not needed at all
* Remove calls to empty protected methods as they are not needed anymore
* Remove non-existant definition for tx_ter_extensionqueue.hidden (DB field does not exist)

[!!!][TASK] Remove code for download counter via SOAP API

See merge request t3o/ter!492

[TASK] Remove database field tx_ter_extensionkeys.maxstoresize

See merge request t3o/ter!493

The database field "tx_ter_extensionkeys.maxstoresize"
is not in use in the whole system and not exposed, so it
can be removed from TCA and the database.

The TER API via SOAP allowed to increase the download counter
for mirrors. However, the mirrorsFrontendUsergroupUid option
was never set since the TER relaunch, so the logic in this
method is removed and returns success for all users, keeping
the API as before.

This change re-implements the generation of the XML file for TYPO3 installations
by moving the relevant code from EXT:ter to ter_fe2.

CombinedExtensionRepository -> does the collection of available extensions
ExtensionIndexService -> handles the XML generation and writing to files

This way, all functionality can be separated and exchanged if necessary.

A CLI command "ter:createExtensionIndexXml" is added which
also shows some more useful output, however the logic is still in
the "UpdateCurrentVersionListTask" class in EXT:ter.

The methods:
tx_ter_helper->requestUpdateOfExtensionIndexFile
tx_ter_helper->writeExtensionIndexfile

are removed, and thus, all of this logic is migrated to Doctrine DBAL.

Root composer.json is adapted so the necessary PHP extensions are available
in your IDE.

[TASK] Remove unused database table tx_ter_extensionmembers

See merge request t3o/ter!490

Resolve "Like an extension throws JS error"

Closes #452

See merge request t3o/ter!487

Show crowdin translation status

See merge request t3o/ter!486

Hide packagist button if no composer is defined

Closes #450

See merge request t3o/ter!484