update install instructions

Author: joeljonsson

INSTALL_INSTRUCTIONS.md

@@ -1,15 +1,17 @@
 # Install instructions for LibAPR.
 
-The way to use it is configure it via some new APR_* variables (can be set to ON/OFF depending on needs) which describes what to build and if it should be installed through cmake commands:
+The build is configured it via several CMake options (APR_* variables), which can be set to ON/OFF depending on your needs.
+The following options control the build type and installation:
 
-APR_BUILD_STATIC_LIB=ON
-APR_BUILD_SHARED_LIB=OFF
-APR_INSTALL=ON
-(all other configuration possibilities are now in the top of CMakeLists.txt file)
+- APR_BUILD_STATIC_LIB=ON
+- APR_BUILD_SHARED_LIB=OFF
+- APR_INSTALL=ON
+
+See [README](README.md) for the full list of build options.
 
 ## OSX / UNIX Installation
 
-so full command line would look like: (-DCMAKE_INSTALL_PREFIX=/tmp/APR can be used for a non-default location)
+The full command-line to install the library may look like:
 
 ```
 mkdir build
@@ -18,35 +20,34 @@ cmake -DAPR_INSTALL=ON -DAPR_BUILD_STATIC_LIB=ON -DAPR_BUILD_SHARED_LIB=OFF ..
 make
 make install
 ```
-
-You may need file-permissions (sudo for the install)
+with other build options turned on/off as required. Non-default install locations can be set via 
+`-DCMAKE_INSTALL_PREFIX=/tmp/APR`. Depending on the location, you may need file-permissions (sudo) for the install command.
 
 ## Windows Installation Clang
 
-``
+On Windows the install commands may look like:
+
+```
 cmake -G "Visual Studio 16 2019" -A x64 -DCMAKE_TOOLCHAIN_FILE="PATH_TO_VCPKG\vcpkg\scripts\buildsystems\vcpkg.cmake" -DVCPKG_TARGET_TRIPLET=x64-windows -T ClangCL -DAPR_BUILD_STATIC_LIB=ON -DAPR_BUILD_SHARED_LIB=OFF -DAPR_INSTALL=ON ..
 cmake --build . --config Release
-``
-
-Need to be in a console running as administrator. 
-
-``
 cmake --install .
-``
+```
 
-## Minimal example CMAKE
+(Probably need to be in a console running as administrator)
 
-To use APR the minimalistic CMakeLists.txt file can be found here: https://github.com/AdaptiveParticles/APR_cpp_project_example
+## Minimal CMake example
 
-##
+A minimalistic CMakeLists.txt file for using LibAPR in another C++ project can be found here: https://github.com/AdaptiveParticles/APR_cpp_project_example
 
-APR::staticLib (Note, tested across Windows, Linux, and Mac)
-APR::sharedLib (Note, not tested)
+### Notes:
 
-If shared version is preferred then APR::sharedLib should be used (and of course APR_BUILD_SHARED_LIB=ON during lib build step).
+If shared version is preferred then `APR::sharedLib` should be used (and of course APR_BUILD_SHARED_LIB=ON during the build step).
 
-NOTICE: if APR is installed in not standard directory then some hint for cmake must be provided by adding install dir to CMAKE_PREFIX_PATH like for above example:
+Use of `APR::staticLib` has been tested across Windows, Linux, and Mac.
+`APR::sharedLib` has currently only been tested on Linux.
 
+If APR is installed in a non-standard location then some hint for cmake must be provided by adding the install directory 
+to CMAKE_PREFIX_PATH, for example:
 ```
 export CMAKE_PREFIX_PATH=/tmp/APR:$CMAKE_PREFIX_PATH
 ```