make license: command to update the license file

This generates a `license.md` file with all the relevant information about
the different libraries and their respecive licenses.

This should replace: THIRD-PARTY-LICENSES.txt

Important files:
* `make_license.py` (main script called by `make license`.
* `licenses.json` (file to add the definition of new licenses).
* `licenses/*/*.txt` (individual license files.

The `license.md` groups the libraries per license, list their
corresponding copyright information and include the complete license.

Code includes contributions from:
* Campbell Barton (multi-line parser for versions.cmake).
* Thomas Dinges (Windows support for `make license`).

Part of: !129018

make.bat

@@ -39,6 +39,11 @@ if "%FORMAT%" == "1" (
 	goto EOF
 )
 
+if "%LICENSE%" == "1" (
+	call "%BLENDER_DIR%\build_files\windows\license.cmd"
+	goto EOF
+)
+
 call "%BLENDER_DIR%\build_files\windows\detect_architecture.cmd"
 if errorlevel 1 goto EOF