Reset filetype and version when changing file selection in tree of backend documents view

[cliffparnitzky]

Reset the filetype and the version when changing the file selection in the tree ...

• check if the name of the selected file is correct formatted
• get filetype and version from filename

Transferred from #3

[cliffparnitzky]

Do not forget to remove the following code after completing this issue and #32: https://github.com/ContaoDMS/dms/blob/master/system/modules/DocumentManagementSystem/dca/tl_dms_documents.php#L571