Revert "Update version to 4.0 to prep for release candidate (#3629)" (#3631)

# Specify the required version of CMake.  If your machine does not

#  have this, it should be easy to build from https://cmake.org/download/

#cmake_minimum_required(VERSION 3.10)

cmake_minimum_required(VERSION 3.10)

# Point cmake to our other CMake files.

list(APPEND CMAKE_MODULE_PATH "${CMAKE_SOURCE_DIR}/cmake")

set(PACKAGE_NAME       "USGS ISIS")

# Version number

set(VERSION            "4.0.0")

set(VERSION            "3.9.1")

set(PACKAGE_VERSION    ${VERSION})

# Full name and version number

# Other release information

string(TIMESTAMP VERSION_DATE "%Y-%m-%d" UTC)

set(RELEASE_STAGE             "beta") # (alpha, beta, stable)

set(RELEASE_STAGE             "stable") # (alpha, beta, stable)

# Define to the address where bug reports for this package should be sent.

set(PACKAGE_BUGREPORT  "https://github.com/USGS-Astrogeology/ISIS3/issues")

#       A Public Release for ISIS3.6.1:                        {% set version = "3.6.1" %}

#       A Release Candidate for ISIS3.6.1:                     {% set version = "3.6.1_RC" %}

#       A custom build of ISIS3.6.1 for the CaSSIS mission:    {% set version = "3.6.1_cassis" %}

{% set version = "4.0.0_RC1" %}

{% set version = "3.9.1" %}

# This is the build number for the current version you are building. If this is the first build of

# this version, the build number will be 0. It is incremented by 1 with every consecutive build of