Add additional information to leafcutter results

[skchronicles]

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Create a new output file combining information from the diff_splicing_cluster_significance.txt output file and information within the prep leafviz Rdata object (see variable called introns). This new file will contain more detailed information pertaining to whether the splice junction is annotated, the gene id of the splice junction, any annotated transcripts with that splice junction, and any exon ids (based on "chr & 3' end position" of the exon for the first feature AND "chr & 5' start position" of the exon for the second feature).

Here are the first few lines of the diff_splicing_cluster_significance.txt:

cluster             status   loglr             df  p                     p.adjust              genes
chr20:clu_59362_NA  Success  19.7040682554871  1   3.43861172147766e-10  2.01968769800836e-06  CDH26
chr20:clu_59363_NA  Success  19.2784852430341  6   8.74089903812546e-07  0.00110014620226997   CDH26

Here is some additional metadata we can pull from the Rdata object, i.e {Case}_vs_{Control}_leafviz.Rdata:

        clusterID  gene          ensemblID   chr    start      end   verdict deltapsi                                       transcripts
clu_59362_NA CDH26 ENSG00000124215.17 chr20 59996588 59999586 annotated   -0.106  ENST00000244049.7+ENST00000350849.10+ENST00000456106.1
clu_59362_NA CDH26 ENSG00000124215.17 chr20 59996761 59999586 annotated    0.106   ENST00000348616.9+ENST00000370991.7+ENST00000497614.1
clu_59363_NA CDH26 ENSG00000124215.17 chr20 59999663 60001343 annotated    0.015                    ENST00000348616.9+ENST00000350849.10