Prevent recursive symlinks

[JakobGM]

Closes #25.

[coveralls]

Pull Request Test Coverage Report for Build 438

• 16 of 16 (100.0%) changed or added relevant lines in 2 files are covered.
• 4 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.01%) to 97.542%

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Files with Coverage Reduction	New Missed Lines	%
astrality/filewatcher.py	4	97.06%
<!--	Total:	4		-->

Totals
Change from base Build 434:	0.01%
Covered Lines:	3690
Relevant Lines:	3783

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💛 - Coveralls

[sshashank124]

If content is A and target is B, and the current set up is:

A (actual data)
B  --->  C (B symlinked to C)
C (another file)

If we execute the symlink action, I tested and it ends up with the following:

A
B  --->  A
B.bak  --->  C
C

So the question is, when dealing with existing symlinks, do we stil want to create a backup of the symlink or just "re-point" the symlink to the new content (since the actual data in C is not actually lost therefore needing a .bak)? Either way, changes look good

[JakobGM]

Good catch! Yes, I think taking backups of existing symlinks seems unecessary, so I added an additional conditional for taking backups.