Open .hash files from system

[nilshenrich]

It should be possible to open .hash files from the system explorer.
When doing so, the file tree hasher shall open and load the opened file automatically.

For this feature, the containing folder shall be loaded automatically and the hash algorithms and comparison inputs shall be set according to the hash file.

The .hash file shall be assigned to be opened with file tree hasher.

[nilshenrich]

Remove file assignment (done for windows) while this enhanced is not done