rfe: easier to read wx map layer list

[hamish]

[moved here from #1051]

for a while I've had the wish to clean up the list of map layers in the main wx display tab as I find it rather cluttering and hard to read.

perhaps: roads @ PERMANENT, or better: roads (PERMANENT)

both in the map layer-list and in the list of maps selector. actually just omit it in the map-selector pull-down list as it is already given by the higher level mapset name heading in the mapset tree (blue text).

... and the (opacity: 100%) [:] stuff would be better packed on the right edge of the row.

thanks, Hamish

[martinl]

see #1100