LSS Zone 1.2.0 alpha 6

New
- segment tracing limit check added to settings and implemented in
'lss_zone_trace_cont.rb'
- 'Help System' updated: screenshots of toolbars updated, info about
internal point element and internal point layer added, information about
nested elements listing added to 'List Zones' chapter, information about
'Settings' dialog added, 'Zone Tool' chapter updated to show information
about 'pick internal point' tool mode, new chapter 'Contour Tracing'
added
- all new strings collected to 'lss_zone.strings'