Add Configuration class

Adding this class improves maintainability by increasing separation
of concern. One major improvement is the removal of reoccuring calls to
loadConfigurations. These calls took a long time. Now it's only called
once.

Tested:
QEMU/yosemite4 with probe statement set to TRUE.
```
root@yosemite4:~# journalctl | grep entity-manager
Dec 19 13:26:21 yosemite4 entity-manager[502]: Clearing previous configuration
Dec 19 13:26:25 yosemite4 entity-manager[502]: Inventory Added: Yosemite 4 Management Board
root@yosemite4:~# busctl tree xyz.openbmc_project.EntityManager
`- /xyz
  `- /xyz/openbmc_project
    |- /xyz/openbmc_project/EntityManager
    `- /xyz/openbmc_project/inventory
      `- /xyz/openbmc_project/inventory/system
        `- /xyz/openbmc_project/inventory/system/board
          `- /xyz/openbmc_project/inventory/system/board/Yosemite_4_Management_Board
            |- /xyz/openbmc_project/inventory/system/board/Yosemite_4_Management_Board/All_Fan
            |- /xyz/openbmc_project/inventory/system/board/Yosemite_4_Management_Board/MGNT_ADC_P0V6_VOLT_V
            |- /xyz/openbmc_project/inventory/system/board/Yosemite_4_Management_Board/MGNT_ADC_P12V_VOLT_V
            |- /xyz/openbmc_project/inventory/system/board/Yosemite_4_Management_Board/MGNT_ADC_P1V0_VOLT_V
            |- /xyz/openbmc_project/inventory/system/board/Yosemite_4_Management_Board/MGNT_ADC_P1V2_VOLT_V
            |- /xyz/openbmc_project/inventory/system/board/Yosemite_4_Management_Board/MGNT_ADC_P1V8_VOLT_V
            |- /xyz/openbmc_project/inventory/system/board/Yosemite_4_Management_Board/MGNT_ADC_P2V5_VOLT_V
            |- /xyz/openbmc_project/inventory/system/board/Yosemite_4_Management_Board/MGNT_ADC_P3V3_RGM_VOLT_V
            |- /xyz/openbmc_project/inventory/system/board/Yosemite_4_Management_Board/MGNT_ADC_P3V3_VOLT_V
            |- /xyz/openbmc_project/inventory/system/board/Yosemite_4_Management_Board/MGNT_ADC_P3V_BAT_VOLT_V
            |- /xyz/openbmc_project/inventory/system/board/Yosemite_4_Management_Board/MGNT_ADC_P5V_USB_VOLT_V
            |- /xyz/openbmc_project/inventory/system/board/Yosemite_4_Management_Board/MGNT_ADC_P5V_VOLT_V
            |- /xyz/openbmc_project/inventory/system/board/Yosemite_4_Management_Board/MGNT_TEMP_C
            |- /xyz/openbmc_project/inventory/system/board/Yosemite_4_Management_Board/PID_NIC_TEMP
            |- /xyz/openbmc_project/inventory/system/board/Yosemite_4_Management_Board/Stepwise_MGNT_TEMP
            |- /xyz/openbmc_project/inventory/system/board/Yosemite_4_Management_Board/Stepwise_NIC_TEMP
            |- /xyz/openbmc_project/inventory/system/board/Yosemite_4_Management_Board/Stepwise_SENTINEL_DOME_SLOT_PRESENT_PERCENTAGE
            `- /xyz/openbmc_project/inventory/system/board/Yosemite_4_Management_Board/Zone_1
```

Change-Id: I5684a03232012e14d97edcf4ea5ed1aed4d50c8d
Signed-off-by: Christopher Meis <christopher.meis@9elements.com>
diff --git a/src/entity_manager/perform_scan.cpp b/src/entity_manager/perform_scan.cpp
index 5e56f9c..c3e5310 100644
--- a/src/entity_manager/perform_scan.cpp
+++ b/src/entity_manager/perform_scan.cpp
@@ -196,7 +196,7 @@
 
 scan::PerformScan::PerformScan(
     EntityManager& em, nlohmann::json& missingConfigurations,
-    std::list<nlohmann::json>& configurations, boost::asio::io_context& io,
+    std::vector<nlohmann::json>& configurations, boost::asio::io_context& io,
     std::function<void()>&& callback) :
     _em(em), _missingConfigurations(missingConfigurations),
     _configurations(configurations), _callback(std::move(callback)), io(io)