Gitools menus

This pull request solves this issues:

1. .tdm export: the file name ends always with .tdm, also if the user didnt specify it.

2. Checking if Gitools is open: A user that clicks in Gitools the link to IGV gets an error message saying where to get IGV in order to run it or the export dialog will be opened.

3. We changed the Gitools menu entries in IGV could include heatmap and/or gene matrix so the user gets an idea what to expect. We would propose something like the following:

> Tools 
>> Gitools heatmaps 
>>> Load gene matrix in Gitools
>>> Export gene matrix (TDM)