ign to gz : Partial Docs Migration and Project Name Followups

[methylDragon]

Part of: #698

These should NOT have any topological dependency!

I migrated a bunch of documentation (.md files, and lots of comments.), including (in a non-exhaustive list):

• ign gazebo invocations in docs
• Many instances of Ignition or ign- (but not all of them)
• Probably a ton more!

After those changes:

$ grep -Eri "ignition" . | wc -l
6940

Note

A couple of other changes are folded into this as well, mostly including follow-ups from the project name migration, these include:

• Libexec directory changes
• GZ_<PROJECT>_PLUGIN_INSTALL_DIR directory changes (ign to gz
• Project name hard-tock notes in Migration.md
• Some headerguards

Pull Requests

• ign -> gz Partial Docs Migration and Project Name Followups : gz-cmake gazebosim/gz-cmake#267
• ign -> gz Partial Docs Migration and Project Name Followups : gz-common gazebosim/gz-common#383
• ign -> gz Partial Docs Migration and Project Name Followups : gz-fuel-tools gazebosim/gz-fuel-tools#268
• ign -> gz Partial Docs Migration and Project Name Followups : gz-gui gazebosim/gz-gui#425
• ign -> gz Partial Docs Migration and Project Name Followups : gz-launch gazebosim/gz-launch#173
• ign -> gz Partial Docs Migration and Project Name Followups : gz-math gazebosim/gz-math#445
• ign -> gz Partial Docs Migration and Project Name Followups : gz-msgs gazebosim/gz-msgs#267
• ign -> gz Partial Docs Migration and Project Name Followups : gz-physics gazebosim/gz-physics#368
• ign -> gz Partial Docs Migration and Project Name Followups : gz-plugin gazebosim/gz-plugin#90
• ign -> gz Partial Docs Migration and Project Name Followups : gz-rendering gazebosim/gz-rendering#657
• ign -> gz Partial Docs Migration and Project Name Followups : gz-sensors gazebosim/gz-sensors#240
• ign -> gz Partial Docs Migration and Project Name Followups : gz-sim gazebosim/gz-sim#1558
• ign -> gz Partial Docs Migration and Project Name Followups : gz-tools gazebosim/gz-tools#98
• ign -> gz Partial Docs Migration and Project Name Followups : gz-transport gazebosim/gz-transport#325
• ign -> gz Partial Docs Migration and Project Name Followups : gz-utils gazebosim/gz-utils#67
• ign -> gz Partial Docs Migration and Project Name Followups : sdformat gazebosim/sdformat#1058