feat: Allow reconfiguration of an existing picomath instance

Keeps track of which operations depend on the configuration and
  invalidates them for lazy reconfiguration when the config changes.

test/custom.js

@@ -46,4 +46,10 @@ describe('Custom instances', () => {
       assert.deepStrictEqual(math.add(math.complex(2,3), math.complex(2,-3)),
          math.complex(4,0))
    })
+
+   it("can be reconfigured", () => {
+      res.reconfigure({resolveComplex: false})
+      assert.deepStrictEqual(math.add(math.complex(2,3), math.complex(2,-3)),
+         math.complex(4,0))
+   })
 })