Fix Linux builds with --opNav True

[scout-andrew]

Linux builds of Basilisk appear to be broken when the opNav flag is used due to a case sensitivity issue. A detailed log of the error is included below.

~/basilisk$  python3 conanfile.py --opNav True --vizInterface True --clean

python -m pip install --upgrade pip
Requirement already satisfied: pip in ./.venv/lib/python3.7/site-packages (23.0)

Configuring: use libstdc++11 by default
Checking conan configuration: Done
Auto-Generating Draft Modules...  Done
Running this conan command:
python -m conans.conan install . --build=missing -s build_type=Release -if dist3/conan -o opNav=True -o vizInterface=True -o buildProject=True -o clean=True
Configuration:
[settings]
arch=x86_64
arch_build=x86_64
build_type=Release
compiler=gcc
compiler.libcxx=libstdc++11
compiler.version=7
os=Linux
os_build=Linux
[options]
buildProject=True
clean=True
opNav=True
vizInterface=True
[build_requires]
[env]
[conf]
tools.system.package_manager:mode=install

[...]

Installing (downloading, building) binaries...
[...]
opencv/4.1.2: Already installed!
[...]

CMake Error at cmake/usingOpenCV.cmake:1 (find_package):
  By not providing "Findopencv.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "opencv", but
  CMake did not find one.

  Could not find a package configuration file provided by "opencv" with any
  of the following names:

    opencvConfig.cmake
    opencv-config.cmake

  Add the installation prefix of "opencv" to CMAKE_PREFIX_PATH or set
  "opencv_DIR" to a directory containing one of the above files.  If "opencv"
  provides a separate development package or SDK, be sure it has been
  installed.
Call Stack (most recent call first):
  simulation/sensors/camera/Custom.cmake:1 (include)
  CMakeLists.txt:336 (include)
  CMakeLists.txt:565 (generate_package_targets)


-- Configuring incomplete, errors occurred!
See also "/home/andrew/basilisk/dist3/CMakeFiles/CMakeOutput.log".
ERROR: conanfile.py (Basilisk/2.1.7b0): Error in build() method, line 265
        cmake.configure()
        ConanException: Error 1 while executing cd '/home/andrew/basilisk/dist3' && cmake -G "Unix Makefiles" -DCMAKE_BUILD_TYPE="Release" -DCONAN_IN_LOCAL_CACHE="OFF" -DCONAN_COMPILER="gcc" -DCONAN_COMPILER_VERSION="7" -DCONAN_CXX_FLAGS="-m64" -DCONAN_SHARED_LINKER_FLAGS="-m64" -DCONAN_C_FLAGS="-m64" -DCMAKE_CXX_FLAGS="-m64" -DCMAKE_SHARED_LINKER_FLAGS="-m64" -DCMAKE_C_FLAGS="-m64" -DCONAN_LIBCXX="libstdc++11" -DCMAKE_INSTALL_PREFIX="/home/andrew/basilisk/package" -DCMAKE_INSTALL_BINDIR="bin" -DCMAKE_INSTALL_SBINDIR="bin" -DCMAKE_INSTALL_LIBEXECDIR="bin" -DCMAKE_INSTALL_LIBDIR="lib" -DCMAKE_INSTALL_INCLUDEDIR="include" -DCMAKE_INSTALL_OLDINCLUDEDIR="include" -DCMAKE_INSTALL_DATAROOTDIR="share" -DCMAKE_PREFIX_PATH="/home/andrew/basilisk/dist3/conan" -DCMAKE_MODULE_PATH="/home/andrew/basilisk/dist3/conan" -DCMAKE_EXPORT_NO_PACKAGE_REGISTRY="ON" -DCONAN_EXPORTED="1" -DBUILD_OPNAV="True" -DBUILD_VIZINTERFACE="True" -DEXTERNAL_MODULES_PATH="" -DPYTHON_VERSION="3.7" -Wno-dev '/home/andrew/basilisk/src'

To reproduce
Steps to reproduce the behavior:

1. Follow documentation for a conventional Linux build
2. Run python3 conanfile.py --opNav True --vizInterface True --clean
3. See error.

Expected behavior
Basilisk builds as normal with the camera and other opNav-related modules

Desktop (please complete the following information):

• OS: Ubuntu
• Version 18.04
• Python version 3.7.15
  Additional config info, such as my conan profile, is provided above.

Additional context
Per #184, this can be fixed with a change to the src/cmake/usingOpenCV.cmake file to reference OpenCV instead of opencv.