Research on automatic locking with office temp files

[juliushaertl]

There are some interesting bits in the sea file implementation about automatically detecting lock files from msoffice/libreoffice

https://github.com/haiwen/seafile/blob/207bd49dcc26ce9600209a7c8720778dd978c5aa/daemon/repo-mgr.c#L3854-L3855

https://github.com/haiwen/seafile/blob/207bd49dcc26ce9600209a7c8720778dd978c5aa/daemon/repo-mgr.c#L3515-L3557

Might be worth to have another look if we can either detect that in the clients and lock the file automatically, or sync the lock files and handle that on the server (that however is currently on the list of ignored files in the client)