build: Added an option to disable UDLs support

Now it is time to get rid of UDLs from tests and examples and then disable them by default.

docs/usage.rst

@@ -123,6 +123,15 @@ It also runs unit tests during Conan build.
 Conan Options
 ^^^^^^^^^^^^^
 
+udls
+++++
+
+**Values**: ``True``/``False``
+
+**Defaulted to**: ``True``
+
+Determines if library should provide User Defined Literals (UDLs) for quantities of various units.
+
 downcast_mode
 +++++++++++++
 
@@ -149,6 +158,16 @@ Additionally, enables project documentation generation when the project is being
 CMake Options
 ^^^^^^^^^^^^^
 
+UNITS_UDLS
++++++++++++++++++++
+
+**Values**: ``ON``/``OFF``
+
+**Defaulted to**: ``ON``
+
+Equivalent to `udls`_.
+
+
 UNITS_DOWNCAST_MODE
 +++++++++++++++++++