[Feat] Startup screen: make location and mapset boxes resizeable

[ninsbl]

Is your feature request related to a problem? Please describe.
With long mapset names, the width of the "box" where mapset are listed can be insufficient to display the full name, e.g. mapset suffixes can become invisible for users.

Describe the solution you'd like
Would be nice if the mapset (and location) box in the startup screen could be resized by the user (e.g. by allowing to move the space between the location and mapset box to either side...).

Describe alternatives you've considered
This is no essential enhancement. So, the alternative is mainly sticking with the current behavior and close the issue as wontfix.

Additional context
See earlier discussion:
https://lists.osgeo.org/pipermail/grass-user/2016-February/073665.html

[petrasovaa]

I understand your need but given the fact we are trying to redo the startup page in the next months, I will close this as wontfix. You can always make the entire window larger.