[!!!][TASK] Drop usage of tx_ter_extensionkeys
The database table tx_ter_extensionkeys containing all registered extensionkeys is dropped in favor of "tx_terfe2_domain_model_extension". This table was synced already anyways, and can now be used within extensions.typo3.org without having to sync with a cronjob anymore. Breaking: The information about "title" and "description" is removed, as it wasn't required via the Web GUI when registering a key already. The sync task / TER importer now only imports the uploaded versions, the SOAP API now creates records directly in tx_terfe2_domain_model_extension when registering a new extension key. The One-Time-Migration-Script by tomalo (ImportAllExtensionKeysTask) is now removed as it is not needed anymore.