Added a new tool - Given an ephemeris source, it finds times when there are more than 12 SVs simultaneously above a specified elevation angle.
Added a new tool - Given an ephemeris source, it finds times when there are more than 12 SVs simultaneously above a specified elevation angle.

git-svn-id: 6625e4d6743179724b113c04fbf297d122273a36@127 108fab2b-820f-0410-9f2c-e5cc2c41d7be

ianmartin/GPSTk,ianmartin/GPSTk,ianmartin/GPSTk,ianmartin/GPSTk,ianmartin/GPSTk,ianmartin/GPSTk