Refactor virtual sensor calculation logic

Refactor the calculation method to calculate.cpp and use std::map
instead of std::array, and other algorithms will be added to
calculate.cpp in the future.

Signed-off-by: George Liu <liuxiwei@ieisystem.com>
Change-Id: I6dcf5119140a5acdf334ebb280dd0b458da1e3ea
diff --git a/meson.build b/meson.build
index bec557a..20d186b 100644
--- a/meson.build
+++ b/meson.build
@@ -24,6 +24,7 @@
 executable(
     'virtual-sensor',
     [
+        'calculate.cpp',
         'virtualSensor.cpp',
         'dbusSensor.cpp',
         'dbusUtils.cpp',