uTorrent ratio issue fixed

The tryFloat function returns 0 if it is fed with a float(!). This resulted in the seed_ratio being set to 0 on first/automatic download. When manually downloading, it did work as the ratio is stored as a string.
Fix untagDir and hastagDir

Changes in commit 8a252bff64b2bb2d376673a0b00e9624d44aaf4c broke the
tagging functionality
Add failsafe for symlink errors

E.g. on Windows you need Admin rights to symlink...