lozusZoom with conditional data

[dariushghasemi]

To draw regional association plot for the conditional dataset in RDS format, we define rules to take proper actions to handle this task. The two main actions are:

1. Extracting conditional dataset for the right COJO variant,
2. Creating an index file readable by locuszoom standalone tool similar to a METAL format.

[dariushghasemi]

Automatic window extension bug in the locusZoom plot fixed!
LocusZoom took by default a window of +/- 200 kb around the reference SNP position, mainly because I did not use -- chr flag along with --beg and --end. Note that --flank 0kb did not solve it earlier.