Rename OwnCloudPlugin to NextcloudPlugin, fixes #19

NextcloudPlugin.class.php

classes/NextcloudFile.php

classes/NextcloudFolder.php

classes/OAuth.class.php

cli/migrate_config_from_owncloud_plugin.php

controllers/configure.php

controllers/file.php

controllers/oauth.php

migrations/01_init_plugin.php

migrations/02_add_unsecure_ssl.php

migrations/03_add_custom_name.php

migrations/04_migrate_plugin_name.php

plugin.manifest

readme.md

views/configure/myarea.php

views/file/edit.php

views/file/update.php