Remove warning filter

The warning should not be filtered. It will only show on older pycrypto
versions where RandomPool had an issue.
Rework sources/sink handling

Paths are now contained in SCPPath objects. At first one object per
path. Later paths from the same user/host pair are put in the same
object.
Simplify check for private keys
Rename from_v/to_v to from_/to_
Simplify parsing of -v option
Add missing module namespace
Conform with flake8
Small modernisation for the pyscp script
Rename parser module to scppath
Change uses of the parser module to use scppath
Use platform independant temp dir on local side
Use unique remote temp files for deployment
Add MIT license