Add gene symbols to merged output

[grst]

Is your feature request related to a problem? Please describe

For downstream analysis it is often useful to have the gene symbols available alongside gene ids.
Adding them later is additional effort and requires knowledge which GTF file was originally used
for the analysis.

Describe the solution you'd like

Add the gene symbols to the salmon.merged.*.tsv (and, in fact, also to the RSEM outputs).
This was already the case before #555.

As a side note:
there are .rds files (which contain the gene symbols) for gene_counts_length_scaled, gene_counts, gene_counts_scaled and transcript_counts, but not for gene_tpm, gene_tpm_scaled and gene_tpm_lengh_scaled.
Maybe this could be made consistent as well.

[lpantano]

Would you be able to run your data with this version: #564, just to make sure the output files are ok now before doing a proper PR?

Thanks!

[grst]

sure, will try it on Monday!

[lpantano]

Well, it is failing ... i forgot to change the R script since I changed the dimension of the table duh! I will fix it on Monday and let you know. Thanks!

[drpatelh]

Assuming this will be closed by #564 ?

[lpantano]

yes

[drpatelh]

Thanks!