macOS installation README update + minor refactor (#81)

* Updated macOS installation steps in README [no ci]

* Refactored installation steps for all OS in README [no ci]

README.md

@@ -26,8 +26,8 @@ To install FastPathology, follow the instructions for your operating system:
   *Note: Windows might prompt you with a security warning, to proceed you must press "More info" followed by "Run anyway".*
 * Run **fastpathology** from your start menu.
 * To **uninstall** the application, go to start menu -> remove programs -> find fastpathology and select uninstall.
-  Optionally you can also delete your C:/Users/"your username"/fastpathology/ which includes stored project results, pipelines and models.
-  And the folder C:/ProgramData/FAST/ which contains a cache.
+  Optionally you can also delete your `C:/Users/"your username"/fastpathology/` which includes stored project results, pipelines, and models.
+  And the folder `C:/ProgramData/FAST/` which contains a cache.
 
 </details>
 
@@ -46,7 +46,7 @@ To install FastPathology, follow the instructions for your operating system:
 ```bash
 sudo dpkg -i fastpathology_ubuntu*.deb
 ```
-* Go to the folder /opt/fastpathology/bin and run the **fastpathology** executable, or run it from the ubuntu menu (windows button->type fastpathology).
+* Go to the folder `/opt/fastpathology/bin/` and run the **fastpathology** executable, or run it from the ubuntu menu (`windows button->type fastpathology`).
 * To **uninstall** the application, run the following in your terminal:
 ```bash
 sudo apt remove fastpathology
@@ -70,16 +70,15 @@ rm -Rf $HOME/FAST
 ```bash
 brew install openslide libomp
 ```
-* Download the tar.xz package from the [release page](https://github.com/AICAN-Research/FAST-Pathology/releases/).
-* Extract the archive to somewhere on your drive
-* Disable the gatekeeper from your terminal:
-```bash
-sudo spctl --master-disable
-```
-* Go to extracted folder and find the bin folder and run the executable **fastpathology**.
+* Download and run the macOS installer (.dmg) from the [release page](https://github.com/AICAN-Research/FAST-Pathology/releases/).
+* In the installer, drag-and-drop the `FastPathology` bundle to the `Applications` directory.
+* When the copy is finished, double-click the `Applications` icon in the installer and right-click + open `FastPathology` from the Applications menu.
+* A warning should be prompted `"macOS cannot verify the developer of FastPathology (...)"`, click `open` and the program should launch.
+
+ *Note: This is only required to be done once. For all future usage, launch FastPathology as a regular App bundle.*
 * To **uninstall** the application, delete the extracted folder.
-  Optionally, you can also delete the  /Users/"your username"/fastpathology folder, which includes stored project results, pipelines and models.
-  And the folder /Users/"your username"/FAST which contains a cache.
+  Optionally, you can also delete the `/Users/"your username"/fastpathology/` folder, which includes stored project results, pipelines, and models.
+  And the folder `/Users/"your username"/FAST/` which contains a cache.
 
 </details>