Microapp BLE - Scanning and filtering advertisements

[martijnvandermarel]

Belongs to https://github.com/crownstone/crownstone-microapp/pull/7

Features:

• Register callbacks in the microapp code for EVT_DEVICE_SCANNED events.
• Forward EVT_DEVICE_SCANNED events to the registered microapp callback.
• Allow starting and stopping forwarding of EVT_DEVICE_SCANNED events from the microapp.
• Add support for logging uint8_t arrays from the microapp in hexadecimal format.

Please check whether the two new CS_TYPEs that were added are added correctly in cs_Types.cpp and cs_StateData.cpp

For testing the branch, see the crownstone-microapp PR referenced above.

[vliedel]

Hey, thanks for your first pull request (with code)!

Since we want to keep or improve the code quality of the firmware, I'm going to be a bit strict, so sorry for that in advance =]

Overall remarks:

• Could you first make sure the current master is merged into this PR, so the merge conflicts are resolved.
• Even if the rest of the file does not, please adhere to the code style. I see not everything is written down, but is done in the example, like allignment should be done with spaces, but indent with tabs.
• Is there a reason you use CMD_BLE_SET_MICROAPP_ISR and CMD_BLE_SET_MICROAPP_CONF instead of direct function calls?
• Make sure you check the command input from the microapp: is the data size correct? are the values ok?
• Directly using CS_TYPE as type in your callback makes CS_TYPE protocol, while currently most of the types are freely editable. I'd suggest making a mapping for the microapps, but it's open for discussion.
• There is no return code for CS_MICROAPP_COMMAND_BLE_SCAN_SET_HANDLER while it can fail if there are already too many isr registered.
• CS_MICROAPP_COMMAND_LOG_ARR implementation should be moved to the log client, right now you need a big buffer on the stack every time, and we try to avoid using sprintf(). However, I think this should be fixed together with the other microapp functions, so doesn't have to be fixed for this merge.
• Move the event handler code into separate functions, now the switch case block has become way too large.
• Prefix microapp structs with microapp so they're not confused with other similar named structs.
• Use nullptr instead of 0 or NULL.