Fix broken logo link

logo64.png was deleted, replaced by wxUiEditor.svg

Merge pull request #1315 from KeyWorksRW/release_prep

1.2.0 Release preparation

Update and add build options

Switch to BUILD_CUSTOM which can be used for building wxWidgets from
a PR or other custom version.

This also adds three options that can be used to conditionalize long-running
features until they are ready to be made available: INTERNAL_FEATURE1,
INTERNAL_FEATURE2 and INTERNAL_FEATURE3.

Change version to 1.1.1, project version to 18.

Update for 1.1 release

Update description and build information

Description adds XRC to the possible outputs. Build information adds C++20
requirement and Windows-only build.

Comment out m_xrcPanel

We're not using this until after 1.0 is released, and in the meantime, it will
break the CodeQL build if used, so remove it.

Switch from WIX to NSIS setup

For what we are installing, NSIS is a better choice. We also now register .wxui files with wxUiEditor and remove that registry on Uninstall.

Closes #1