Allow users to specify sample names

[mattravenhall]

Currently sample names are pulled from input vcf files by assuming they are given as full paths with only one full stop character. This works in most cases, but will fail if user vcf contain multiple full stops, or a user short-hands their path (ie. ./thisfile.vcf). This method also restricts users who with to redefine their sample names from non-file names.

To resolve this, I plan to allow for a special column in the subPops file (ie. named 'SampleID') which will link file locations to custom IDs.

[mattravenhall]

SV-Pop is now robust to additional 'full-stops' in paths, though it is advised to use full paths where possible.