add gene annotations: RSAT gene

[weiju]

Supporting gene annotations can be helpful when generating the cmonkey2 output, e.g. to show the user hints about the gene they are looking at.

We need to support this as optional annotations, which e.g. can be then extracted from the RSAT file or others. We will start with RSAT genes first and then build on that.

For visualizing this, cmviewer should have e.g. tool tips on the genes.